260223:1415 20260223 nextJS & nestJS Best pratices
All checks were successful
Build and Deploy / deploy (push) Successful in 4m44s

This commit is contained in:
admin
2026-02-23 14:15:06 +07:00
parent c90a664f53
commit ef16817f38
164 changed files with 24815 additions and 311 deletions

View File

@@ -0,0 +1,153 @@
---
name: next-best-practices
description: Next.js best practices - file conventions, RSC boundaries, data patterns, async APIs, metadata, error handling, route handlers, image/font optimization, bundling
user-invocable: false
---
# Next.js Best Practices
Apply these rules when writing or reviewing Next.js code.
## File Conventions
See [file-conventions.md](./file-conventions.md) for:
- Project structure and special files
- Route segments (dynamic, catch-all, groups)
- Parallel and intercepting routes
- Middleware rename in v16 (middleware → proxy)
## RSC Boundaries
Detect invalid React Server Component patterns.
See [rsc-boundaries.md](./rsc-boundaries.md) for:
- Async client component detection (invalid)
- Non-serializable props detection
- Server Action exceptions
## Async Patterns
Next.js 15+ async API changes.
See [async-patterns.md](./async-patterns.md) for:
- Async `params` and `searchParams`
- Async `cookies()` and `headers()`
- Migration codemod
## Runtime Selection
See [runtime-selection.md](./runtime-selection.md) for:
- Default to Node.js runtime
- When Edge runtime is appropriate
## Directives
See [directives.md](./directives.md) for:
- `'use client'`, `'use server'` (React)
- `'use cache'` (Next.js)
## Functions
See [functions.md](./functions.md) for:
- Navigation hooks: `useRouter`, `usePathname`, `useSearchParams`, `useParams`
- Server functions: `cookies`, `headers`, `draftMode`, `after`
- Generate functions: `generateStaticParams`, `generateMetadata`
## Error Handling
See [error-handling.md](./error-handling.md) for:
- `error.tsx`, `global-error.tsx`, `not-found.tsx`
- `redirect`, `permanentRedirect`, `notFound`
- `forbidden`, `unauthorized` (auth errors)
- `unstable_rethrow` for catch blocks
## Data Patterns
See [data-patterns.md](./data-patterns.md) for:
- Server Components vs Server Actions vs Route Handlers
- Avoiding data waterfalls (`Promise.all`, Suspense, preload)
- Client component data fetching
## Route Handlers
See [route-handlers.md](./route-handlers.md) for:
- `route.ts` basics
- GET handler conflicts with `page.tsx`
- Environment behavior (no React DOM)
- When to use vs Server Actions
## Metadata & OG Images
See [metadata.md](./metadata.md) for:
- Static and dynamic metadata
- `generateMetadata` function
- OG image generation with `next/og`
- File-based metadata conventions
## Image Optimization
See [image.md](./image.md) for:
- Always use `next/image` over `<img>`
- Remote images configuration
- Responsive `sizes` attribute
- Blur placeholders
- Priority loading for LCP
## Font Optimization
See [font.md](./font.md) for:
- `next/font` setup
- Google Fonts, local fonts
- Tailwind CSS integration
- Preloading subsets
## Bundling
See [bundling.md](./bundling.md) for:
- Server-incompatible packages
- CSS imports (not link tags)
- Polyfills (already included)
- ESM/CommonJS issues
- Bundle analysis
## Scripts
See [scripts.md](./scripts.md) for:
- `next/script` vs native script tags
- Inline scripts need `id`
- Loading strategies
- Google Analytics with `@next/third-parties`
## Hydration Errors
See [hydration-error.md](./hydration-error.md) for:
- Common causes (browser APIs, dates, invalid HTML)
- Debugging with error overlay
- Fixes for each cause
## Suspense Boundaries
See [suspense-boundaries.md](./suspense-boundaries.md) for:
- CSR bailout with `useSearchParams` and `usePathname`
- Which hooks require Suspense boundaries
## Parallel & Intercepting Routes
See [parallel-routes.md](./parallel-routes.md) for:
- Modal patterns with `@slot` and `(.)` interceptors
- `default.tsx` for fallbacks
- Closing modals correctly with `router.back()`
## Self-Hosting
See [self-hosting.md](./self-hosting.md) for:
- `output: 'standalone'` for Docker
- Cache handlers for multi-instance ISR
- What works vs needs extra setup
## Debug Tricks
See [debug-tricks.md](./debug-tricks.md) for:
- MCP endpoint for AI-assisted debugging
- Rebuild specific routes with `--debug-build-paths`

View File

@@ -0,0 +1,87 @@
# Async Patterns
In Next.js 15+, `params`, `searchParams`, `cookies()`, and `headers()` are asynchronous.
## Async Params and SearchParams
Always type them as `Promise<...>` and await them.
### Pages and Layouts
```tsx
type Props = { params: Promise<{ slug: string }> }
export default async function Page({ params }: Props) {
const { slug } = await params
}
```
### Route Handlers
```tsx
export async function GET(
request: Request,
{ params }: { params: Promise<{ id: string }> }
) {
const { id } = await params
}
```
### SearchParams
```tsx
type Props = {
params: Promise<{ slug: string }>
searchParams: Promise<{ query?: string }>
}
export default async function Page({ params, searchParams }: Props) {
const { slug } = await params
const { query } = await searchParams
}
```
### Synchronous Components
Use `React.use()` for non-async components:
```tsx
import { use } from 'react'
type Props = { params: Promise<{ slug: string }> }
export default function Page({ params }: Props) {
const { slug } = use(params)
}
```
### generateMetadata
```tsx
type Props = { params: Promise<{ slug: string }> }
export async function generateMetadata({ params }: Props): Promise<Metadata> {
const { slug } = await params
return { title: slug }
}
```
## Async Cookies and Headers
```tsx
import { cookies, headers } from 'next/headers'
export default async function Page() {
const cookieStore = await cookies()
const headersList = await headers()
const theme = cookieStore.get('theme')
const userAgent = headersList.get('user-agent')
}
```
## Migration Codemod
```bash
npx @next/codemod@latest next-async-request-api .
```

View File

@@ -0,0 +1,180 @@
# Bundling
Fix common bundling issues with third-party packages.
## Server-Incompatible Packages
Some packages use browser APIs (`window`, `document`, `localStorage`) and fail in Server Components.
### Error Signs
```
ReferenceError: window is not defined
ReferenceError: document is not defined
ReferenceError: localStorage is not defined
Module not found: Can't resolve 'fs'
```
### Solution 1: Mark as Client-Only
If the package is only needed on client:
```tsx
// Bad: Fails - package uses window
import SomeChart from 'some-chart-library'
export default function Page() {
return <SomeChart />
}
// Good: Use dynamic import with ssr: false
import dynamic from 'next/dynamic'
const SomeChart = dynamic(() => import('some-chart-library'), {
ssr: false,
})
export default function Page() {
return <SomeChart />
}
```
### Solution 2: Externalize from Server Bundle
For packages that should run on server but have bundling issues:
```js
// next.config.js
module.exports = {
serverExternalPackages: ['problematic-package'],
}
```
Use this for:
- Packages with native bindings (sharp, bcrypt)
- Packages that don't bundle well (some ORMs)
- Packages with circular dependencies
### Solution 3: Client Component Wrapper
Wrap the entire usage in a client component:
```tsx
// components/ChartWrapper.tsx
'use client'
import { Chart } from 'chart-library'
export function ChartWrapper(props) {
return <Chart {...props} />
}
// app/page.tsx (server component)
import { ChartWrapper } from '@/components/ChartWrapper'
export default function Page() {
return <ChartWrapper data={data} />
}
```
## CSS Imports
Import CSS files instead of using `<link>` tags. Next.js handles bundling and optimization.
```tsx
// Bad: Manual link tag
<link rel="stylesheet" href="/styles.css" />
// Good: Import CSS
import './styles.css'
// Good: CSS Modules
import styles from './Button.module.css'
```
## Polyfills
Next.js includes common polyfills automatically. Don't load redundant ones from polyfill.io or similar CDNs.
Already included: `Array.from`, `Object.assign`, `Promise`, `fetch`, `Map`, `Set`, `Symbol`, `URLSearchParams`, and 50+ others.
```tsx
// Bad: Redundant polyfills
<script src="https://polyfill.io/v3/polyfill.min.js?features=fetch,Promise,Array.from" />
// Good: Next.js includes these automatically
```
## ESM/CommonJS Issues
### Error Signs
```
SyntaxError: Cannot use import statement outside a module
Error: require() of ES Module
Module not found: ESM packages need to be imported
```
### Solution: Transpile Package
```js
// next.config.js
module.exports = {
transpilePackages: ['some-esm-package', 'another-package'],
}
```
## Common Problematic Packages
| Package | Issue | Solution |
|---------|-------|----------|
| `sharp` | Native bindings | `serverExternalPackages: ['sharp']` |
| `bcrypt` | Native bindings | `serverExternalPackages: ['bcrypt']` or use `bcryptjs` |
| `canvas` | Native bindings | `serverExternalPackages: ['canvas']` |
| `recharts` | Uses window | `dynamic(() => import('recharts'), { ssr: false })` |
| `react-quill` | Uses document | `dynamic(() => import('react-quill'), { ssr: false })` |
| `mapbox-gl` | Uses window | `dynamic(() => import('mapbox-gl'), { ssr: false })` |
| `monaco-editor` | Uses window | `dynamic(() => import('@monaco-editor/react'), { ssr: false })` |
| `lottie-web` | Uses document | `dynamic(() => import('lottie-react'), { ssr: false })` |
## Bundle Analysis
Analyze bundle size with the built-in analyzer (Next.js 16.1+):
```bash
next experimental-analyze
```
This opens an interactive UI to:
- Filter by route, environment (client/server), and type
- Inspect module sizes and import chains
- View treemap visualization
Save output for comparison:
```bash
next experimental-analyze --output
# Output saved to .next/diagnostics/analyze
```
Reference: https://nextjs.org/docs/app/guides/package-bundling
## Migrating from Webpack to Turbopack
Turbopack is the default bundler in Next.js 15+. If you have custom webpack config, migrate to Turbopack-compatible alternatives:
```js
// next.config.js
module.exports = {
// Good: Works with Turbopack
serverExternalPackages: ['package'],
transpilePackages: ['package'],
// Bad: Webpack-only - migrate away from this
webpack: (config) => {
// custom webpack config
},
}
```
Reference: https://nextjs.org/docs/app/building-your-application/upgrading/from-webpack-to-turbopack

View File

@@ -0,0 +1,297 @@
# Data Patterns
Choose the right data fetching pattern for each use case.
## Decision Tree
```
Need to fetch data?
├── From a Server Component?
│ └── Use: Fetch directly (no API needed)
├── From a Client Component?
│ ├── Is it a mutation (POST/PUT/DELETE)?
│ │ └── Use: Server Action
│ └── Is it a read (GET)?
│ └── Use: Route Handler OR pass from Server Component
├── Need external API access (webhooks, third parties)?
│ └── Use: Route Handler
└── Need REST API for mobile app / external clients?
└── Use: Route Handler
```
## Pattern 1: Server Components (Preferred for Reads)
Fetch data directly in Server Components - no API layer needed.
```tsx
// app/users/page.tsx
async function UsersPage() {
// Direct database access - no API round-trip
const users = await db.user.findMany();
// Or fetch from external API
const posts = await fetch('https://api.example.com/posts').then(r => r.json());
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
**Benefits**:
- No API to maintain
- No client-server waterfall
- Secrets stay on server
- Direct database access
## Pattern 2: Server Actions (Preferred for Mutations)
Server Actions are the recommended way to handle mutations.
```tsx
// app/actions.ts
'use server';
import { revalidatePath } from 'next/cache';
export async function createPost(formData: FormData) {
const title = formData.get('title') as string;
await db.post.create({ data: { title } });
revalidatePath('/posts');
}
export async function deletePost(id: string) {
await db.post.delete({ where: { id } });
revalidateTag('posts');
}
```
```tsx
// app/posts/new/page.tsx
import { createPost } from '@/app/actions';
export default function NewPost() {
return (
<form action={createPost}>
<input name="title" required />
<button type="submit">Create</button>
</form>
);
}
```
**Benefits**:
- End-to-end type safety
- Progressive enhancement (works without JS)
- Automatic request handling
- Integrated with React transitions
**Constraints**:
- POST only (no GET caching semantics)
- Internal use only (no external access)
- Cannot return non-serializable data
## Pattern 3: Route Handlers (APIs)
Use Route Handlers when you need a REST API.
```tsx
// app/api/posts/route.ts
import { NextRequest, NextResponse } from 'next/server';
// GET is cacheable
export async function GET(request: NextRequest) {
const posts = await db.post.findMany();
return NextResponse.json(posts);
}
// POST for mutations
export async function POST(request: NextRequest) {
const body = await request.json();
const post = await db.post.create({ data: body });
return NextResponse.json(post, { status: 201 });
}
```
**When to use**:
- External API access (mobile apps, third parties)
- Webhooks from external services
- GET endpoints that need HTTP caching
- OpenAPI/Swagger documentation needed
**When NOT to use**:
- Internal data fetching (use Server Components)
- Mutations from your UI (use Server Actions)
## Avoiding Data Waterfalls
### Problem: Sequential Fetches
```tsx
// Bad: Sequential waterfalls
async function Dashboard() {
const user = await getUser(); // Wait...
const posts = await getPosts(); // Then wait...
const comments = await getComments(); // Then wait...
return <div>...</div>;
}
```
### Solution 1: Parallel Fetching with Promise.all
```tsx
// Good: Parallel fetching
async function Dashboard() {
const [user, posts, comments] = await Promise.all([
getUser(),
getPosts(),
getComments(),
]);
return <div>...</div>;
}
```
### Solution 2: Streaming with Suspense
```tsx
// Good: Show content progressively
import { Suspense } from 'react';
async function Dashboard() {
return (
<div>
<Suspense fallback={<UserSkeleton />}>
<UserSection />
</Suspense>
<Suspense fallback={<PostsSkeleton />}>
<PostsSection />
</Suspense>
</div>
);
}
async function UserSection() {
const user = await getUser(); // Fetches independently
return <div>{user.name}</div>;
}
async function PostsSection() {
const posts = await getPosts(); // Fetches independently
return <PostList posts={posts} />;
}
```
### Solution 3: Preload Pattern
```tsx
// lib/data.ts
import { cache } from 'react';
export const getUser = cache(async (id: string) => {
return db.user.findUnique({ where: { id } });
});
export const preloadUser = (id: string) => {
void getUser(id); // Fire and forget
};
```
```tsx
// app/user/[id]/page.tsx
import { getUser, preloadUser } from '@/lib/data';
export default async function UserPage({ params }) {
const { id } = await params;
// Start fetching early
preloadUser(id);
// Do other work...
// Data likely ready by now
const user = await getUser(id);
return <div>{user.name}</div>;
}
```
## Client Component Data Fetching
When Client Components need data:
### Option 1: Pass from Server Component (Preferred)
```tsx
// Server Component
async function Page() {
const data = await fetchData();
return <ClientComponent initialData={data} />;
}
// Client Component
'use client';
function ClientComponent({ initialData }) {
const [data, setData] = useState(initialData);
// ...
}
```
### Option 2: Fetch on Mount (When Necessary)
```tsx
'use client';
import { useEffect, useState } from 'react';
function ClientComponent() {
const [data, setData] = useState(null);
useEffect(() => {
fetch('/api/data')
.then(r => r.json())
.then(setData);
}, []);
if (!data) return <Loading />;
return <div>{data.value}</div>;
}
```
### Option 3: Server Action for Reads (Works But Not Ideal)
Server Actions can be called from Client Components for reads, but this is not their intended purpose:
```tsx
'use client';
import { getData } from './actions';
import { useEffect, useState } from 'react';
function ClientComponent() {
const [data, setData] = useState(null);
useEffect(() => {
getData().then(setData);
}, []);
return <div>{data?.value}</div>;
}
```
**Note**: Server Actions always use POST, so no HTTP caching. Prefer Route Handlers for cacheable reads.
## Quick Reference
| Pattern | Use Case | HTTP Method | Caching |
|---------|----------|-------------|---------|
| Server Component fetch | Internal reads | Any | Full Next.js caching |
| Server Action | Mutations, form submissions | POST only | No |
| Route Handler | External APIs, webhooks | Any | GET can be cached |
| Client fetch to API | Client-side reads | Any | HTTP cache headers |

View File

@@ -0,0 +1,105 @@
# Debug Tricks
Tricks to speed up debugging Next.js applications.
## MCP Endpoint (Dev Server)
Next.js exposes a `/_next/mcp` endpoint in development for AI-assisted debugging via MCP (Model Context Protocol).
- **Next.js 16+**: Enabled by default, use `next-devtools-mcp`
- **Next.js < 16**: Requires `experimental.mcpServer: true` in next.config.js
Reference: https://nextjs.org/docs/app/guides/mcp
**Important**: Find the actual port of the running Next.js dev server (check terminal output or `package.json` scripts). Don't assume port 3000.
### Request Format
The endpoint uses JSON-RPC 2.0 over HTTP POST:
```bash
curl -X POST http://localhost:<port>/_next/mcp \
-H "Content-Type: application/json" \
-H "Accept: application/json, text/event-stream" \
-d '{
"jsonrpc": "2.0",
"id": "1",
"method": "tools/call",
"params": {
"name": "<tool-name>",
"arguments": {}
}
}'
```
### Available Tools
#### `get_errors`
Get current errors from dev server (build errors, runtime errors with source-mapped stacks):
```json
{ "name": "get_errors", "arguments": {} }
```
#### `get_routes`
Discover all routes by scanning filesystem:
```json
{ "name": "get_routes", "arguments": {} }
// Optional: { "name": "get_routes", "arguments": { "routerType": "app" } }
```
Returns: `{ "appRouter": ["/", "/api/users/[id]", ...], "pagesRouter": [...] }`
#### `get_project_metadata`
Get project path and dev server URL:
```json
{ "name": "get_project_metadata", "arguments": {} }
```
Returns: `{ "projectPath": "/path/to/project", "devServerUrl": "http://localhost:3000" }`
#### `get_page_metadata`
Get runtime metadata about current page render (requires active browser session):
```json
{ "name": "get_page_metadata", "arguments": {} }
```
Returns segment trie data showing layouts, boundaries, and page components.
#### `get_logs`
Get path to Next.js development log file:
```json
{ "name": "get_logs", "arguments": {} }
```
Returns path to `<distDir>/logs/next-development.log`
#### `get_server_action_by_id`
Locate a Server Action by ID:
```json
{ "name": "get_server_action_by_id", "arguments": { "actionId": "<action-id>" } }
```
### Example: Get Errors
```bash
curl -X POST http://localhost:<port>/_next/mcp \
-H "Content-Type: application/json" \
-H "Accept: application/json, text/event-stream" \
-d '{"jsonrpc":"2.0","id":"1","method":"tools/call","params":{"name":"get_errors","arguments":{}}}'
```
## Rebuild Specific Routes (Next.js 16+)
Use `--debug-build-paths` to rebuild only specific routes instead of the entire app:
```bash
# Rebuild a specific route
next build --debug-build-paths "/dashboard"
# Rebuild routes matching a glob
next build --debug-build-paths "/api/*"
# Dynamic routes
next build --debug-build-paths "/blog/[slug]"
```
Use this to:
- Quickly verify a build fix without full rebuild
- Debug static generation issues for specific pages
- Iterate faster on build errors

View File

@@ -0,0 +1,73 @@
# Directives
## React Directives
These are React directives, not Next.js specific.
### `'use client'`
Marks a component as a Client Component. Required for:
- React hooks (`useState`, `useEffect`, etc.)
- Event handlers (`onClick`, `onChange`)
- Browser APIs (`window`, `localStorage`)
```tsx
'use client'
import { useState } from 'react'
export function Counter() {
const [count, setCount] = useState(0)
return <button onClick={() => setCount(count + 1)}>{count}</button>
}
```
Reference: https://react.dev/reference/rsc/use-client
### `'use server'`
Marks a function as a Server Action. Can be passed to Client Components.
```tsx
'use server'
export async function submitForm(formData: FormData) {
// Runs on server
}
```
Or inline within a Server Component:
```tsx
export default function Page() {
async function submit() {
'use server'
// Runs on server
}
return <form action={submit}>...</form>
}
```
Reference: https://react.dev/reference/rsc/use-server
---
## Next.js Directive
### `'use cache'`
Marks a function or component for caching. Part of Next.js Cache Components.
```tsx
'use cache'
export async function getCachedData() {
return await fetchData()
}
```
Requires `cacheComponents: true` in `next.config.ts`.
For detailed usage including cache profiles, `cacheLife()`, `cacheTag()`, and `updateTag()`, see the `next-cache-components` skill.
Reference: https://nextjs.org/docs/app/api-reference/directives/use-cache

View File

@@ -0,0 +1,227 @@
# Error Handling
Handle errors gracefully in Next.js applications.
Reference: https://nextjs.org/docs/app/getting-started/error-handling
## Error Boundaries
### `error.tsx`
Catches errors in a route segment and its children:
```tsx
'use client'
export default function Error({
error,
reset,
}: {
error: Error & { digest?: string }
reset: () => void
}) {
return (
<div>
<h2>Something went wrong!</h2>
<button onClick={() => reset()}>Try again</button>
</div>
)
}
```
**Important:** `error.tsx` must be a Client Component.
### `global-error.tsx`
Catches errors in root layout:
```tsx
'use client'
export default function GlobalError({
error,
reset,
}: {
error: Error & { digest?: string }
reset: () => void
}) {
return (
<html>
<body>
<h2>Something went wrong!</h2>
<button onClick={() => reset()}>Try again</button>
</body>
</html>
)
}
```
**Important:** Must include `<html>` and `<body>` tags.
## Server Actions: Navigation API Gotcha
**Do NOT wrap navigation APIs in try-catch.** They throw special errors that Next.js handles internally.
Reference: https://nextjs.org/docs/app/api-reference/functions/redirect#behavior
```tsx
'use server'
import { redirect } from 'next/navigation'
import { notFound } from 'next/navigation'
// Bad: try-catch catches the navigation "error"
async function createPost(formData: FormData) {
try {
const post = await db.post.create({ ... })
redirect(`/posts/${post.id}`) // This throws!
} catch (error) {
// redirect() throw is caught here - navigation fails!
return { error: 'Failed to create post' }
}
}
// Good: Call navigation APIs outside try-catch
async function createPost(formData: FormData) {
let post
try {
post = await db.post.create({ ... })
} catch (error) {
return { error: 'Failed to create post' }
}
redirect(`/posts/${post.id}`) // Outside try-catch
}
// Good: Re-throw navigation errors
async function createPost(formData: FormData) {
try {
const post = await db.post.create({ ... })
redirect(`/posts/${post.id}`)
} catch (error) {
if (error instanceof Error && error.message === 'NEXT_REDIRECT') {
throw error // Re-throw navigation errors
}
return { error: 'Failed to create post' }
}
}
```
Same applies to:
- `redirect()` - 307 temporary redirect
- `permanentRedirect()` - 308 permanent redirect
- `notFound()` - 404 not found
- `forbidden()` - 403 forbidden
- `unauthorized()` - 401 unauthorized
Use `unstable_rethrow()` to re-throw these errors in catch blocks:
```tsx
import { unstable_rethrow } from 'next/navigation'
async function action() {
try {
// ...
redirect('/success')
} catch (error) {
unstable_rethrow(error) // Re-throws Next.js internal errors
return { error: 'Something went wrong' }
}
}
```
## Redirects
```tsx
import { redirect, permanentRedirect } from 'next/navigation'
// 307 Temporary - use for most cases
redirect('/new-path')
// 308 Permanent - use for URL migrations (cached by browsers)
permanentRedirect('/new-url')
```
## Auth Errors
Trigger auth-related error pages:
```tsx
import { forbidden, unauthorized } from 'next/navigation'
async function Page() {
const session = await getSession()
if (!session) {
unauthorized() // Renders unauthorized.tsx (401)
}
if (!session.hasAccess) {
forbidden() // Renders forbidden.tsx (403)
}
return <Dashboard />
}
```
Create corresponding error pages:
```tsx
// app/forbidden.tsx
export default function Forbidden() {
return <div>You don't have access to this resource</div>
}
// app/unauthorized.tsx
export default function Unauthorized() {
return <div>Please log in to continue</div>
}
```
## Not Found
### `not-found.tsx`
Custom 404 page for a route segment:
```tsx
export default function NotFound() {
return (
<div>
<h2>Not Found</h2>
<p>Could not find the requested resource</p>
</div>
)
}
```
### Triggering Not Found
```tsx
import { notFound } from 'next/navigation'
export default async function Page({ params }: { params: Promise<{ id: string }> }) {
const { id } = await params
const post = await getPost(id)
if (!post) {
notFound() // Renders closest not-found.tsx
}
return <div>{post.title}</div>
}
```
## Error Hierarchy
Errors bubble up to the nearest error boundary:
```
app/
├── error.tsx # Catches errors from all children
├── blog/
│ ├── error.tsx # Catches errors in /blog/*
│ └── [slug]/
│ ├── error.tsx # Catches errors in /blog/[slug]
│ └── page.tsx
└── layout.tsx # Errors here go to global-error.tsx
```

View File

@@ -0,0 +1,140 @@
# File Conventions
Next.js App Router uses file-based routing with special file conventions.
## Project Structure
Reference: https://nextjs.org/docs/app/getting-started/project-structure
```
app/
├── layout.tsx # Root layout (required)
├── page.tsx # Home page (/)
├── loading.tsx # Loading UI
├── error.tsx # Error UI
├── not-found.tsx # 404 UI
├── global-error.tsx # Global error UI
├── route.ts # API endpoint
├── template.tsx # Re-rendered layout
├── default.tsx # Parallel route fallback
├── blog/
│ ├── page.tsx # /blog
│ └── [slug]/
│ └── page.tsx # /blog/:slug
└── (group)/ # Route group (no URL impact)
└── page.tsx
```
## Special Files
| File | Purpose |
|------|---------|
| `page.tsx` | UI for a route segment |
| `layout.tsx` | Shared UI for segment and children |
| `loading.tsx` | Loading UI (Suspense boundary) |
| `error.tsx` | Error UI (Error boundary) |
| `not-found.tsx` | 404 UI |
| `route.ts` | API endpoint |
| `template.tsx` | Like layout but re-renders on navigation |
| `default.tsx` | Fallback for parallel routes |
## Route Segments
```
app/
├── blog/ # Static segment: /blog
├── [slug]/ # Dynamic segment: /:slug
├── [...slug]/ # Catch-all: /a/b/c
├── [[...slug]]/ # Optional catch-all: / or /a/b/c
└── (marketing)/ # Route group (ignored in URL)
```
## Parallel Routes
```
app/
├── @analytics/
│ └── page.tsx
├── @sidebar/
│ └── page.tsx
└── layout.tsx # Receives { analytics, sidebar } as props
```
## Intercepting Routes
```
app/
├── feed/
│ └── page.tsx
├── @modal/
│ └── (.)photo/[id]/ # Intercepts /photo/[id] from /feed
│ └── page.tsx
└── photo/[id]/
└── page.tsx
```
Conventions:
- `(.)` - same level
- `(..)` - one level up
- `(..)(..)` - two levels up
- `(...)` - from root
## Private Folders
```
app/
├── _components/ # Private folder (not a route)
│ └── Button.tsx
└── page.tsx
```
Prefix with `_` to exclude from routing.
## Middleware / Proxy
### Next.js 14-15: `middleware.ts`
```ts
// middleware.ts (root of project)
import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';
export function middleware(request: NextRequest) {
// Auth, redirects, rewrites, etc.
return NextResponse.next();
}
export const config = {
matcher: ['/dashboard/:path*', '/api/:path*'],
};
```
### Next.js 16+: `proxy.ts`
Renamed for clarity - same capabilities, different names:
```ts
// proxy.ts (root of project)
import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';
export function proxy(request: NextRequest) {
// Same logic as middleware
return NextResponse.next();
}
export const proxyConfig = {
matcher: ['/dashboard/:path*', '/api/:path*'],
};
```
| Version | File | Export | Config |
|---------|------|--------|--------|
| v14-15 | `middleware.ts` | `middleware()` | `config` |
| v16+ | `proxy.ts` | `proxy()` | `proxyConfig` |
**Migration**: Run `npx @next/codemod@latest upgrade` to auto-rename.
## File Conventions Reference
Reference: https://nextjs.org/docs/app/api-reference/file-conventions

View File

@@ -0,0 +1,245 @@
# Font Optimization
Use `next/font` for automatic font optimization with zero layout shift.
## Google Fonts
```tsx
// app/layout.tsx
import { Inter } from 'next/font/google'
const inter = Inter({ subsets: ['latin'] })
export default function RootLayout({ children }: { children: React.ReactNode }) {
return (
<html lang="en" className={inter.className}>
<body>{children}</body>
</html>
)
}
```
## Multiple Fonts
```tsx
import { Inter, Roboto_Mono } from 'next/font/google'
const inter = Inter({
subsets: ['latin'],
variable: '--font-inter',
})
const robotoMono = Roboto_Mono({
subsets: ['latin'],
variable: '--font-roboto-mono',
})
export default function RootLayout({ children }: { children: React.ReactNode }) {
return (
<html lang="en" className={`${inter.variable} ${robotoMono.variable}`}>
<body>{children}</body>
</html>
)
}
```
Use in CSS:
```css
body {
font-family: var(--font-inter);
}
code {
font-family: var(--font-roboto-mono);
}
```
## Font Weights and Styles
```tsx
// Single weight
const inter = Inter({
subsets: ['latin'],
weight: '400',
})
// Multiple weights
const inter = Inter({
subsets: ['latin'],
weight: ['400', '500', '700'],
})
// Variable font (recommended) - includes all weights
const inter = Inter({
subsets: ['latin'],
// No weight needed - variable fonts support all weights
})
// With italic
const inter = Inter({
subsets: ['latin'],
style: ['normal', 'italic'],
})
```
## Local Fonts
```tsx
import localFont from 'next/font/local'
const myFont = localFont({
src: './fonts/MyFont.woff2',
})
// Multiple files for different weights
const myFont = localFont({
src: [
{
path: './fonts/MyFont-Regular.woff2',
weight: '400',
style: 'normal',
},
{
path: './fonts/MyFont-Bold.woff2',
weight: '700',
style: 'normal',
},
],
})
// Variable font
const myFont = localFont({
src: './fonts/MyFont-Variable.woff2',
variable: '--font-my-font',
})
```
## Tailwind CSS Integration
```tsx
// app/layout.tsx
import { Inter } from 'next/font/google'
const inter = Inter({
subsets: ['latin'],
variable: '--font-inter',
})
export default function RootLayout({ children }) {
return (
<html lang="en" className={inter.variable}>
<body>{children}</body>
</html>
)
}
```
```js
// tailwind.config.js
module.exports = {
theme: {
extend: {
fontFamily: {
sans: ['var(--font-inter)'],
},
},
},
}
```
## Preloading Subsets
Only load needed character subsets:
```tsx
// Latin only (most common)
const inter = Inter({ subsets: ['latin'] })
// Multiple subsets
const inter = Inter({ subsets: ['latin', 'latin-ext', 'cyrillic'] })
```
## Display Strategy
Control font loading behavior:
```tsx
const inter = Inter({
subsets: ['latin'],
display: 'swap', // Default - shows fallback, swaps when loaded
})
// Options:
// 'auto' - browser decides
// 'block' - short block period, then swap
// 'swap' - immediate fallback, swap when ready (recommended)
// 'fallback' - short block, short swap, then fallback
// 'optional' - short block, no swap (use if font is optional)
```
## Don't Use Manual Font Links
Always use `next/font` instead of `<link>` tags for Google Fonts.
```tsx
// Bad: Manual link tag (blocks rendering, no optimization)
<link href="https://fonts.googleapis.com/css2?family=Inter" rel="stylesheet" />
// Bad: Missing display and preconnect
<link href="https://fonts.googleapis.com/css2?family=Inter" rel="stylesheet" />
// Good: Use next/font (self-hosted, zero layout shift)
import { Inter } from 'next/font/google'
const inter = Inter({ subsets: ['latin'] })
```
## Common Mistakes
```tsx
// Bad: Importing font in every component
// components/Button.tsx
import { Inter } from 'next/font/google'
const inter = Inter({ subsets: ['latin'] }) // Creates new instance each time!
// Good: Import once in layout, use CSS variable
// app/layout.tsx
const inter = Inter({ subsets: ['latin'], variable: '--font-inter' })
// Bad: Using @import in CSS (blocks rendering)
/* globals.css */
@import url('https://fonts.googleapis.com/css2?family=Inter');
// Good: Use next/font (self-hosted, no network request)
import { Inter } from 'next/font/google'
// Bad: Loading all weights when only using a few
const inter = Inter({ subsets: ['latin'] }) // Loads all weights
// Good: Specify only needed weights (for non-variable fonts)
const inter = Inter({ subsets: ['latin'], weight: ['400', '700'] })
// Bad: Missing subset - loads all characters
const inter = Inter({})
// Good: Always specify subset
const inter = Inter({ subsets: ['latin'] })
```
## Font in Specific Components
```tsx
// For component-specific fonts, export from a shared file
// lib/fonts.ts
import { Inter, Playfair_Display } from 'next/font/google'
export const inter = Inter({ subsets: ['latin'], variable: '--font-inter' })
export const playfair = Playfair_Display({ subsets: ['latin'], variable: '--font-playfair' })
// components/Heading.tsx
import { playfair } from '@/lib/fonts'
export function Heading({ children }) {
return <h1 className={playfair.className}>{children}</h1>
}
```

View File

@@ -0,0 +1,108 @@
# Functions
Next.js function APIs.
Reference: https://nextjs.org/docs/app/api-reference/functions
## Navigation Hooks (Client)
| Hook | Purpose | Reference |
|------|---------|-----------|
| `useRouter` | Programmatic navigation (`push`, `replace`, `back`, `refresh`) | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-router) |
| `usePathname` | Get current pathname | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-pathname) |
| `useSearchParams` | Read URL search parameters | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-search-params) |
| `useParams` | Access dynamic route parameters | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-params) |
| `useSelectedLayoutSegment` | Active child segment (one level) | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-selected-layout-segment) |
| `useSelectedLayoutSegments` | All active segments below layout | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-selected-layout-segments) |
| `useLinkStatus` | Check link prefetch status | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-link-status) |
| `useReportWebVitals` | Report Core Web Vitals metrics | [Docs](https://nextjs.org/docs/app/api-reference/functions/use-report-web-vitals) |
## Server Functions
| Function | Purpose | Reference |
|----------|---------|-----------|
| `cookies` | Read/write cookies | [Docs](https://nextjs.org/docs/app/api-reference/functions/cookies) |
| `headers` | Read request headers | [Docs](https://nextjs.org/docs/app/api-reference/functions/headers) |
| `draftMode` | Enable preview of unpublished CMS content | [Docs](https://nextjs.org/docs/app/api-reference/functions/draft-mode) |
| `after` | Run code after response finishes streaming | [Docs](https://nextjs.org/docs/app/api-reference/functions/after) |
| `connection` | Wait for connection before dynamic rendering | [Docs](https://nextjs.org/docs/app/api-reference/functions/connection) |
| `userAgent` | Parse User-Agent header | [Docs](https://nextjs.org/docs/app/api-reference/functions/userAgent) |
## Generate Functions
| Function | Purpose | Reference |
|----------|---------|-----------|
| `generateStaticParams` | Pre-render dynamic routes at build time | [Docs](https://nextjs.org/docs/app/api-reference/functions/generate-static-params) |
| `generateMetadata` | Dynamic metadata | [Docs](https://nextjs.org/docs/app/api-reference/functions/generate-metadata) |
| `generateViewport` | Dynamic viewport config | [Docs](https://nextjs.org/docs/app/api-reference/functions/generate-viewport) |
| `generateSitemaps` | Multiple sitemaps for large sites | [Docs](https://nextjs.org/docs/app/api-reference/functions/generate-sitemaps) |
| `generateImageMetadata` | Multiple OG images per route | [Docs](https://nextjs.org/docs/app/api-reference/functions/generate-image-metadata) |
## Request/Response
| Function | Purpose | Reference |
|----------|---------|-----------|
| `NextRequest` | Extended Request with helpers | [Docs](https://nextjs.org/docs/app/api-reference/functions/next-request) |
| `NextResponse` | Extended Response with helpers | [Docs](https://nextjs.org/docs/app/api-reference/functions/next-response) |
| `ImageResponse` | Generate OG images | [Docs](https://nextjs.org/docs/app/api-reference/functions/image-response) |
## Common Examples
### Navigation
Use `next/link` for internal navigation instead of `<a>` tags.
```tsx
// Bad: Plain anchor tag
<a href="/about">About</a>
// Good: Next.js Link
import Link from 'next/link'
<Link href="/about">About</Link>
```
Active link styling:
```tsx
'use client'
import Link from 'next/link'
import { usePathname } from 'next/navigation'
export function NavLink({ href, children }) {
const pathname = usePathname()
return (
<Link href={href} className={pathname === href ? 'active' : ''}>
{children}
</Link>
)
}
```
### Static Generation
```tsx
// app/blog/[slug]/page.tsx
export async function generateStaticParams() {
const posts = await getPosts()
return posts.map((post) => ({ slug: post.slug }))
}
```
### After Response
```tsx
import { after } from 'next/server'
export async function POST(request: Request) {
const data = await processRequest(request)
after(async () => {
await logAnalytics(data)
})
return Response.json({ success: true })
}
```

View File

@@ -0,0 +1,91 @@
# Hydration Errors
Diagnose and fix React hydration mismatch errors.
## Error Signs
- "Hydration failed because the initial UI does not match"
- "Text content does not match server-rendered HTML"
## Debugging
In development, click the hydration error to see the server/client diff.
## Common Causes and Fixes
### Browser-only APIs
```tsx
// Bad: Causes mismatch - window doesn't exist on server
<div>{window.innerWidth}</div>
// Good: Use client component with mounted check
'use client'
import { useState, useEffect } from 'react'
export function ClientOnly({ children }: { children: React.ReactNode }) {
const [mounted, setMounted] = useState(false)
useEffect(() => setMounted(true), [])
return mounted ? children : null
}
```
### Date/Time Rendering
Server and client may be in different timezones:
```tsx
// Bad: Causes mismatch
<span>{new Date().toLocaleString()}</span>
// Good: Render on client only
'use client'
const [time, setTime] = useState<string>()
useEffect(() => setTime(new Date().toLocaleString()), [])
```
### Random Values or IDs
```tsx
// Bad: Random values differ between server and client
<div id={Math.random().toString()}>
// Good: Use useId hook
import { useId } from 'react'
function Input() {
const id = useId()
return <input id={id} />
}
```
### Invalid HTML Nesting
```tsx
// Bad: Invalid - div inside p
<p><div>Content</div></p>
// Bad: Invalid - p inside p
<p><p>Nested</p></p>
// Good: Valid nesting
<div><p>Content</p></div>
```
### Third-party Scripts
Scripts that modify DOM during hydration.
```tsx
// Good: Use next/script with afterInteractive
import Script from 'next/script'
export default function Page() {
return (
<Script
src="https://example.com/script.js"
strategy="afterInteractive"
/>
)
}
```

View File

@@ -0,0 +1,173 @@
# Image Optimization
Use `next/image` for automatic image optimization.
## Always Use next/image
```tsx
// Bad: Avoid native img
<img src="/hero.png" alt="Hero" />
// Good: Use next/image
import Image from 'next/image'
<Image src="/hero.png" alt="Hero" width={800} height={400} />
```
## Required Props
Images need explicit dimensions to prevent layout shift:
```tsx
// Local images - dimensions inferred automatically
import heroImage from './hero.png'
<Image src={heroImage} alt="Hero" />
// Remote images - must specify width/height
<Image src="https://example.com/image.jpg" alt="Hero" width={800} height={400} />
// Or use fill for parent-relative sizing
<div style={{ position: 'relative', width: '100%', height: 400 }}>
<Image src="/hero.png" alt="Hero" fill style={{ objectFit: 'cover' }} />
</div>
```
## Remote Images Configuration
Remote domains must be configured in `next.config.js`:
```js
// next.config.js
module.exports = {
images: {
remotePatterns: [
{
protocol: 'https',
hostname: 'example.com',
pathname: '/images/**',
},
{
protocol: 'https',
hostname: '*.cdn.com', // Wildcard subdomain
},
],
},
}
```
## Responsive Images
Use `sizes` to tell the browser which size to download:
```tsx
// Full-width hero
<Image
src="/hero.png"
alt="Hero"
fill
sizes="100vw"
/>
// Responsive grid (3 columns on desktop, 1 on mobile)
<Image
src="/card.png"
alt="Card"
fill
sizes="(max-width: 768px) 100vw, 33vw"
/>
// Fixed sidebar image
<Image
src="/avatar.png"
alt="Avatar"
width={200}
height={200}
sizes="200px"
/>
```
## Blur Placeholder
Prevent layout shift with placeholders:
```tsx
// Local images - automatic blur hash
import heroImage from './hero.png'
<Image src={heroImage} alt="Hero" placeholder="blur" />
// Remote images - provide blurDataURL
<Image
src="https://example.com/image.jpg"
alt="Hero"
width={800}
height={400}
placeholder="blur"
blurDataURL="data:image/jpeg;base64,/9j/4AAQSkZJRg..."
/>
// Or use color placeholder
<Image
src="https://example.com/image.jpg"
alt="Hero"
width={800}
height={400}
placeholder="empty"
style={{ backgroundColor: '#e0e0e0' }}
/>
```
## Priority Loading
Use `priority` for above-the-fold images (LCP):
```tsx
// Hero image - loads immediately
<Image src="/hero.png" alt="Hero" fill priority />
// Below-fold images - lazy loaded by default (no priority needed)
<Image src="/card.png" alt="Card" width={400} height={300} />
```
## Common Mistakes
```tsx
// Bad: Missing sizes with fill - downloads largest image
<Image src="/hero.png" alt="Hero" fill />
// Good: Add sizes for proper responsive behavior
<Image src="/hero.png" alt="Hero" fill sizes="100vw" />
// Bad: Using width/height for aspect ratio only
<Image src="/hero.png" alt="Hero" width={16} height={9} />
// Good: Use actual display dimensions or fill with sizes
<Image src="/hero.png" alt="Hero" fill sizes="100vw" style={{ objectFit: 'cover' }} />
// Bad: Remote image without config
<Image src="https://untrusted.com/image.jpg" alt="Image" width={400} height={300} />
// Error: Invalid src prop, hostname not configured
// Good: Add hostname to next.config.js remotePatterns
```
## Static Export
When using `output: 'export'`, use `unoptimized` or custom loader:
```tsx
// Option 1: Disable optimization
<Image src="/hero.png" alt="Hero" width={800} height={400} unoptimized />
// Option 2: Global config
// next.config.js
module.exports = {
output: 'export',
images: { unoptimized: true },
}
// Option 3: Custom loader (Cloudinary, Imgix, etc.)
const cloudinaryLoader = ({ src, width, quality }) => {
return `https://res.cloudinary.com/demo/image/upload/w_${width},q_${quality || 75}/${src}`
}
<Image loader={cloudinaryLoader} src="sample.jpg" alt="Sample" width={800} height={400} />
```

View File

@@ -0,0 +1,301 @@
# Metadata
Add SEO metadata to Next.js pages using the Metadata API.
## Important: Server Components Only
The `metadata` object and `generateMetadata` function are **only supported in Server Components**. They cannot be used in Client Components.
If the target page has `'use client'`:
1. Remove `'use client'` if possible, move client logic to child components
2. Or extract metadata to a parent Server Component layout
3. Or split the file: Server Component with metadata imports Client Components
## Static Metadata
```tsx
import type { Metadata } from 'next'
export const metadata: Metadata = {
title: 'Page Title',
description: 'Page description for search engines',
}
```
## Dynamic Metadata
```tsx
import type { Metadata } from 'next'
type Props = { params: Promise<{ slug: string }> }
export async function generateMetadata({ params }: Props): Promise<Metadata> {
const { slug } = await params
const post = await getPost(slug)
return { title: post.title, description: post.description }
}
```
## Avoid Duplicate Fetches
Use React `cache()` when the same data is needed for both metadata and page:
```tsx
import { cache } from 'react'
export const getPost = cache(async (slug: string) => {
return await db.posts.findFirst({ where: { slug } })
})
```
## Viewport
Separate from metadata for streaming support:
```tsx
import type { Viewport } from 'next'
export const viewport: Viewport = {
width: 'device-width',
initialScale: 1,
themeColor: '#000000',
}
// Or dynamic
export function generateViewport({ params }): Viewport {
return { themeColor: getThemeColor(params) }
}
```
## Title Templates
In root layout for consistent naming:
```tsx
export const metadata: Metadata = {
title: { default: 'Site Name', template: '%s | Site Name' },
}
```
## Metadata File Conventions
Reference: https://nextjs.org/docs/app/getting-started/project-structure#metadata-file-conventions
Place these files in `app/` directory (or route segments):
| File | Purpose |
|------|---------|
| `favicon.ico` | Favicon |
| `icon.png` / `icon.svg` | App icon |
| `apple-icon.png` | Apple app icon |
| `opengraph-image.png` | OG image |
| `twitter-image.png` | Twitter card image |
| `sitemap.ts` / `sitemap.xml` | Sitemap (use `generateSitemaps` for multiple) |
| `robots.ts` / `robots.txt` | Robots directives |
| `manifest.ts` / `manifest.json` | Web app manifest |
## SEO Best Practice: Static Files Are Often Enough
For most sites, **static metadata files provide excellent SEO coverage**:
```
app/
├── favicon.ico
├── opengraph-image.png # Works for both OG and Twitter
├── sitemap.ts
├── robots.ts
└── layout.tsx # With title/description metadata
```
**Tips:**
- A single `opengraph-image.png` covers both Open Graph and Twitter (Twitter falls back to OG)
- Static `title` and `description` in layout metadata is sufficient for most pages
- Only use dynamic `generateMetadata` when content varies per page
---
# OG Image Generation
Generate dynamic Open Graph images using `next/og`.
## Important Rules
1. **Use `next/og`** - not `@vercel/og` (it's built into Next.js)
2. **No searchParams** - OG images can't access search params, use route params instead
3. **Avoid Edge runtime** - Use default Node.js runtime
```tsx
// Good
import { ImageResponse } from 'next/og'
// Bad
// import { ImageResponse } from '@vercel/og'
// export const runtime = 'edge'
```
## Basic OG Image
```tsx
// app/opengraph-image.tsx
import { ImageResponse } from 'next/og'
export const alt = 'Site Name'
export const size = { width: 1200, height: 630 }
export const contentType = 'image/png'
export default function Image() {
return new ImageResponse(
(
<div
style={{
fontSize: 128,
background: 'white',
width: '100%',
height: '100%',
display: 'flex',
alignItems: 'center',
justifyContent: 'center',
}}
>
Hello World
</div>
),
{ ...size }
)
}
```
## Dynamic OG Image
```tsx
// app/blog/[slug]/opengraph-image.tsx
import { ImageResponse } from 'next/og'
export const alt = 'Blog Post'
export const size = { width: 1200, height: 630 }
export const contentType = 'image/png'
type Props = { params: Promise<{ slug: string }> }
export default async function Image({ params }: Props) {
const { slug } = await params
const post = await getPost(slug)
return new ImageResponse(
(
<div
style={{
fontSize: 48,
background: 'linear-gradient(to bottom, #1a1a1a, #333)',
color: 'white',
width: '100%',
height: '100%',
display: 'flex',
flexDirection: 'column',
alignItems: 'center',
justifyContent: 'center',
padding: 48,
}}
>
<div style={{ fontSize: 64, fontWeight: 'bold' }}>{post.title}</div>
<div style={{ marginTop: 24, opacity: 0.8 }}>{post.description}</div>
</div>
),
{ ...size }
)
}
```
## Custom Fonts
```tsx
import { ImageResponse } from 'next/og'
import { join } from 'path'
import { readFile } from 'fs/promises'
export default async function Image() {
const fontPath = join(process.cwd(), 'assets/fonts/Inter-Bold.ttf')
const fontData = await readFile(fontPath)
return new ImageResponse(
(
<div style={{ fontFamily: 'Inter', fontSize: 64 }}>
Custom Font Text
</div>
),
{
width: 1200,
height: 630,
fonts: [{ name: 'Inter', data: fontData, style: 'normal' }],
}
)
}
```
## File Naming
- `opengraph-image.tsx` - Open Graph (Facebook, LinkedIn)
- `twitter-image.tsx` - Twitter/X cards (optional, falls back to OG)
## Styling Notes
ImageResponse uses Flexbox layout:
- Use `display: 'flex'`
- No CSS Grid support
- Styles must be inline objects
## Multiple OG Images
Use `generateImageMetadata` for multiple images per route:
```tsx
// app/blog/[slug]/opengraph-image.tsx
import { ImageResponse } from 'next/og'
export async function generateImageMetadata({ params }) {
const images = await getPostImages(params.slug)
return images.map((img, idx) => ({
id: idx,
alt: img.alt,
size: { width: 1200, height: 630 },
contentType: 'image/png',
}))
}
export default async function Image({ params, id }) {
const images = await getPostImages(params.slug)
const image = images[id]
return new ImageResponse(/* ... */)
}
```
## Multiple Sitemaps
Use `generateSitemaps` for large sites:
```tsx
// app/sitemap.ts
import type { MetadataRoute } from 'next'
export async function generateSitemaps() {
// Return array of sitemap IDs
return [{ id: 0 }, { id: 1 }, { id: 2 }]
}
export default async function sitemap({
id,
}: {
id: number
}): Promise<MetadataRoute.Sitemap> {
const start = id * 50000
const end = start + 50000
const products = await getProducts(start, end)
return products.map((product) => ({
url: `https://example.com/product/${product.id}`,
lastModified: product.updatedAt,
}))
}
```
Generates `/sitemap/0.xml`, `/sitemap/1.xml`, etc.

View File

@@ -0,0 +1,287 @@
# Parallel & Intercepting Routes
Parallel routes render multiple pages in the same layout. Intercepting routes show a different UI when navigating from within your app vs direct URL access. Together they enable modal patterns.
## File Structure
```
app/
├── @modal/ # Parallel route slot
│ ├── default.tsx # Required! Returns null
│ ├── (.)photos/ # Intercepts /photos/*
│ │ └── [id]/
│ │ └── page.tsx # Modal content
│ └── [...]catchall/ # Optional: catch unmatched
│ └── page.tsx
├── photos/
│ └── [id]/
│ └── page.tsx # Full page (direct access)
├── layout.tsx # Renders both children and @modal
└── page.tsx
```
## Step 1: Root Layout with Slot
```tsx
// app/layout.tsx
export default function RootLayout({
children,
modal,
}: {
children: React.ReactNode;
modal: React.ReactNode;
}) {
return (
<html>
<body>
{children}
{modal}
</body>
</html>
);
}
```
## Step 2: Default File (Critical!)
**Every parallel route slot MUST have a `default.tsx`** to prevent 404s on hard navigation.
```tsx
// app/@modal/default.tsx
export default function Default() {
return null;
}
```
Without this file, refreshing any page will 404 because Next.js can't determine what to render in the `@modal` slot.
## Step 3: Intercepting Route (Modal)
The `(.)` prefix intercepts routes at the same level.
```tsx
// app/@modal/(.)photos/[id]/page.tsx
import { Modal } from '@/components/modal';
export default async function PhotoModal({
params
}: {
params: Promise<{ id: string }>
}) {
const { id } = await params;
const photo = await getPhoto(id);
return (
<Modal>
<img src={photo.url} alt={photo.title} />
</Modal>
);
}
```
## Step 4: Full Page (Direct Access)
```tsx
// app/photos/[id]/page.tsx
export default async function PhotoPage({
params
}: {
params: Promise<{ id: string }>
}) {
const { id } = await params;
const photo = await getPhoto(id);
return (
<div className="full-page">
<img src={photo.url} alt={photo.title} />
<h1>{photo.title}</h1>
</div>
);
}
```
## Step 5: Modal Component with Correct Closing
**Critical: Use `router.back()` to close modals, NOT `router.push()` or `<Link>`.**
```tsx
// components/modal.tsx
'use client';
import { useRouter } from 'next/navigation';
import { useCallback, useEffect, useRef } from 'react';
export function Modal({ children }: { children: React.ReactNode }) {
const router = useRouter();
const overlayRef = useRef<HTMLDivElement>(null);
// Close on escape key
useEffect(() => {
function onKeyDown(e: KeyboardEvent) {
if (e.key === 'Escape') {
router.back(); // Correct
}
}
document.addEventListener('keydown', onKeyDown);
return () => document.removeEventListener('keydown', onKeyDown);
}, [router]);
// Close on overlay click
const handleOverlayClick = useCallback((e: React.MouseEvent) => {
if (e.target === overlayRef.current) {
router.back(); // Correct
}
}, [router]);
return (
<div
ref={overlayRef}
onClick={handleOverlayClick}
className="fixed inset-0 bg-black/50 flex items-center justify-center z-50"
>
<div className="bg-white rounded-lg p-6 max-w-2xl w-full mx-4">
<button
onClick={() => router.back()} // Correct!
className="absolute top-4 right-4"
>
Close
</button>
{children}
</div>
</div>
);
}
```
### Why NOT `router.push('/')` or `<Link href="/">`?
Using `push` or `Link` to "close" a modal:
1. Adds a new history entry (back button shows modal again)
2. Doesn't properly clear the intercepted route
3. Can cause the modal to flash or persist unexpectedly
`router.back()` correctly:
1. Removes the intercepted route from history
2. Returns to the previous page
3. Properly unmounts the modal
## Route Matcher Reference
Matchers match **route segments**, not filesystem paths:
| Matcher | Matches | Example |
|---------|---------|---------|
| `(.)` | Same level | `@modal/(.)photos` intercepts `/photos` |
| `(..)` | One level up | `@modal/(..)settings` from `/dashboard/@modal` intercepts `/settings` |
| `(..)(..)` | Two levels up | Rarely used |
| `(...)` | From root | `@modal/(...)photos` intercepts `/photos` from anywhere |
**Common mistake**: Thinking `(..)` means "parent folder" - it means "parent route segment".
## Handling Hard Navigation
When users directly visit `/photos/123` (bookmark, refresh, shared link):
- The intercepting route is bypassed
- The full `photos/[id]/page.tsx` renders
- Modal doesn't appear (expected behavior)
If you want the modal to appear on direct access too, you need additional logic:
```tsx
// app/photos/[id]/page.tsx
import { Modal } from '@/components/modal';
export default async function PhotoPage({ params }) {
const { id } = await params;
const photo = await getPhoto(id);
// Option: Render as modal on direct access too
return (
<Modal>
<img src={photo.url} alt={photo.title} />
</Modal>
);
}
```
## Common Gotchas
### 1. Missing `default.tsx` → 404 on Refresh
Every `@slot` folder needs a `default.tsx` that returns `null` (or appropriate content).
### 2. Modal Persists After Navigation
You're using `router.push()` instead of `router.back()`.
### 3. Nested Parallel Routes Need Defaults Too
If you have `@modal` inside a route group, each level needs its own `default.tsx`:
```
app/
├── (marketing)/
│ ├── @modal/
│ │ └── default.tsx # Needed!
│ └── layout.tsx
└── layout.tsx
```
### 4. Intercepted Route Shows Wrong Content
Check your matcher:
- `(.)photos` intercepts `/photos` from the same route level
- If your `@modal` is in `app/dashboard/@modal`, use `(.)photos` to intercept `/dashboard/photos`, not `/photos`
### 5. TypeScript Errors with `params`
In Next.js 15+, `params` is a Promise:
```tsx
// Correct
export default async function Page({ params }: { params: Promise<{ id: string }> }) {
const { id } = await params;
}
```
## Complete Example: Photo Gallery Modal
```
app/
├── @modal/
│ ├── default.tsx
│ └── (.)photos/
│ └── [id]/
│ └── page.tsx
├── photos/
│ ├── page.tsx # Gallery grid
│ └── [id]/
│ └── page.tsx # Full photo page
├── layout.tsx
└── page.tsx
```
Links in the gallery:
```tsx
// app/photos/page.tsx
import Link from 'next/link';
export default async function Gallery() {
const photos = await getPhotos();
return (
<div className="grid grid-cols-3 gap-4">
{photos.map(photo => (
<Link key={photo.id} href={`/photos/${photo.id}`}>
<img src={photo.thumbnail} alt={photo.title} />
</Link>
))}
</div>
);
}
```
Clicking a photo → Modal opens (intercepted)
Direct URL → Full page renders
Refresh while modal open → Full page renders

View File

@@ -0,0 +1,146 @@
# Route Handlers
Create API endpoints with `route.ts` files.
## Basic Usage
```tsx
// app/api/users/route.ts
export async function GET() {
const users = await getUsers()
return Response.json(users)
}
export async function POST(request: Request) {
const body = await request.json()
const user = await createUser(body)
return Response.json(user, { status: 201 })
}
```
## Supported Methods
`GET`, `POST`, `PUT`, `PATCH`, `DELETE`, `HEAD`, `OPTIONS`
## GET Handler Conflicts with page.tsx
**A `route.ts` and `page.tsx` cannot coexist in the same folder.**
```
app/
├── api/
│ └── users/
│ └── route.ts # /api/users
└── users/
├── page.tsx # /users (page)
└── route.ts # Warning: Conflicts with page.tsx!
```
If you need both a page and an API at the same path, use different paths:
```
app/
├── users/
│ └── page.tsx # /users (page)
└── api/
└── users/
└── route.ts # /api/users (API)
```
## Environment Behavior
Route handlers run in a **Server Component-like environment**:
- Yes: Can use `async/await`
- Yes: Can access `cookies()`, `headers()`
- Yes: Can use Node.js APIs
- No: Cannot use React hooks
- No: Cannot use React DOM APIs
- No: Cannot use browser APIs
```tsx
// Bad: This won't work - no React DOM in route handlers
import { renderToString } from 'react-dom/server'
export async function GET() {
const html = renderToString(<Component />) // Error!
return new Response(html)
}
```
## Dynamic Route Handlers
```tsx
// app/api/users/[id]/route.ts
export async function GET(
request: Request,
{ params }: { params: Promise<{ id: string }> }
) {
const { id } = await params
const user = await getUser(id)
if (!user) {
return Response.json({ error: 'Not found' }, { status: 404 })
}
return Response.json(user)
}
```
## Request Helpers
```tsx
export async function GET(request: Request) {
// URL and search params
const { searchParams } = new URL(request.url)
const query = searchParams.get('q')
// Headers
const authHeader = request.headers.get('authorization')
// Cookies (Next.js helper)
const cookieStore = await cookies()
const token = cookieStore.get('token')
return Response.json({ query, token })
}
```
## Response Helpers
```tsx
// JSON response
return Response.json({ data })
// With status
return Response.json({ error: 'Not found' }, { status: 404 })
// With headers
return Response.json(data, {
headers: {
'Cache-Control': 'max-age=3600',
},
})
// Redirect
return Response.redirect(new URL('/login', request.url))
// Stream
return new Response(stream, {
headers: { 'Content-Type': 'text/event-stream' },
})
```
## When to Use Route Handlers vs Server Actions
| Use Case | Route Handlers | Server Actions |
|----------|----------------|----------------|
| Form submissions | No | Yes |
| Data mutations from UI | No | Yes |
| Third-party webhooks | Yes | No |
| External API consumption | Yes | No |
| Public REST API | Yes | No |
| File uploads | Both work | Both work |
**Prefer Server Actions** for mutations triggered from your UI.
**Use Route Handlers** for external integrations and public APIs.

View File

@@ -0,0 +1,159 @@
# RSC Boundaries
Detect and prevent invalid patterns when crossing Server/Client component boundaries.
## Detection Rules
### 1. Async Client Components Are Invalid
Client components **cannot** be async functions. Only Server Components can be async.
**Detect:** File has `'use client'` AND component is `async function` or returns `Promise`
```tsx
// Bad: async client component
'use client'
export default async function UserProfile() {
const user = await getUser() // Cannot await in client component
return <div>{user.name}</div>
}
// Good: Remove async, fetch data in parent server component
// page.tsx (server component - no 'use client')
export default async function Page() {
const user = await getUser()
return <UserProfile user={user} />
}
// UserProfile.tsx (client component)
'use client'
export function UserProfile({ user }: { user: User }) {
return <div>{user.name}</div>
}
```
```tsx
// Bad: async arrow function client component
'use client'
const Dashboard = async () => {
const data = await fetchDashboard()
return <div>{data}</div>
}
// Good: Fetch in server component, pass data down
```
### 2. Non-Serializable Props to Client Components
Props passed from Server → Client must be JSON-serializable.
**Detect:** Server component passes these to a client component:
- Functions (except Server Actions with `'use server'`)
- `Date` objects
- `Map`, `Set`, `WeakMap`, `WeakSet`
- Class instances
- `Symbol` (unless globally registered)
- Circular references
```tsx
// Bad: Function prop
// page.tsx (server)
export default function Page() {
const handleClick = () => console.log('clicked')
return <ClientButton onClick={handleClick} />
}
// Good: Define function inside client component
// ClientButton.tsx
'use client'
export function ClientButton() {
const handleClick = () => console.log('clicked')
return <button onClick={handleClick}>Click</button>
}
```
```tsx
// Bad: Date object (silently becomes string, then crashes)
// page.tsx (server)
export default async function Page() {
const post = await getPost()
return <PostCard createdAt={post.createdAt} /> // Date object
}
// PostCard.tsx (client) - will crash on .getFullYear()
'use client'
export function PostCard({ createdAt }: { createdAt: Date }) {
return <span>{createdAt.getFullYear()}</span> // Runtime error!
}
// Good: Serialize to string on server
// page.tsx (server)
export default async function Page() {
const post = await getPost()
return <PostCard createdAt={post.createdAt.toISOString()} />
}
// PostCard.tsx (client)
'use client'
export function PostCard({ createdAt }: { createdAt: string }) {
const date = new Date(createdAt)
return <span>{date.getFullYear()}</span>
}
```
```tsx
// Bad: Class instance
const user = new UserModel(data)
<ClientProfile user={user} /> // Methods will be stripped
// Good: Pass plain object
const user = await getUser()
<ClientProfile user={{ id: user.id, name: user.name }} />
```
```tsx
// Bad: Map/Set
<ClientComponent items={new Map([['a', 1]])} />
// Good: Convert to array/object
<ClientComponent items={Object.fromEntries(map)} />
<ClientComponent items={Array.from(set)} />
```
### 3. Server Actions Are the Exception
Functions marked with `'use server'` CAN be passed to client components.
```tsx
// Valid: Server Action can be passed
// actions.ts
'use server'
export async function submitForm(formData: FormData) {
// server-side logic
}
// page.tsx (server)
import { submitForm } from './actions'
export default function Page() {
return <ClientForm onSubmit={submitForm} /> // OK!
}
// ClientForm.tsx (client)
'use client'
export function ClientForm({ onSubmit }: { onSubmit: (data: FormData) => Promise<void> }) {
return <form action={onSubmit}>...</form>
}
```
## Quick Reference
| Pattern | Valid? | Fix |
|---------|--------|-----|
| `'use client'` + `async function` | No | Fetch in server parent, pass data |
| Pass `() => {}` to client | No | Define in client or use server action |
| Pass `new Date()` to client | No | Use `.toISOString()` |
| Pass `new Map()` to client | No | Convert to object/array |
| Pass class instance to client | No | Pass plain object |
| Pass server action to client | Yes | - |
| Pass `string/number/boolean` | Yes | - |
| Pass plain object/array | Yes | - |

View File

@@ -0,0 +1,39 @@
# Runtime Selection
## Use Node.js Runtime by Default
Use the default Node.js runtime for new routes and pages. Only use Edge runtime if the project already uses it or there's a specific requirement.
```tsx
// Good: Default - no runtime config needed (uses Node.js)
export default function Page() { ... }
// Caution: Only if already used in project or specifically required
export const runtime = 'edge'
```
## When to Use Each
### Node.js Runtime (Default)
- Full Node.js API support
- File system access (`fs`)
- Full `crypto` support
- Database connections
- Most npm packages work
### Edge Runtime
- Only for specific edge-location latency requirements
- Limited API (no `fs`, limited `crypto`)
- Smaller cold start
- Geographic distribution needs
## Detection
**Before adding `runtime = 'edge'`**, check:
1. Does the project already use Edge runtime?
2. Is there a specific latency requirement?
3. Are all dependencies Edge-compatible?
If unsure, use Node.js runtime.

View File

@@ -0,0 +1,141 @@
# Scripts
Loading third-party scripts in Next.js.
## Use next/script
Always use `next/script` instead of native `<script>` tags for better performance.
```tsx
// Bad: Native script tag
<script src="https://example.com/script.js"></script>
// Good: Next.js Script component
import Script from 'next/script'
<Script src="https://example.com/script.js" />
```
## Inline Scripts Need ID
Inline scripts require an `id` attribute for Next.js to track them.
```tsx
// Bad: Missing id
<Script dangerouslySetInnerHTML={{ __html: 'console.log("hi")' }} />
// Good: Has id
<Script id="my-script" dangerouslySetInnerHTML={{ __html: 'console.log("hi")' }} />
// Good: Inline with id
<Script id="show-banner">
{`document.getElementById('banner').classList.remove('hidden')`}
</Script>
```
## Don't Put Script in Head
`next/script` should not be placed inside `next/head`. It handles its own positioning.
```tsx
// Bad: Script inside Head
import Head from 'next/head'
import Script from 'next/script'
<Head>
<Script src="/analytics.js" />
</Head>
// Good: Script outside Head
<Head>
<title>Page</title>
</Head>
<Script src="/analytics.js" />
```
## Loading Strategies
```tsx
// afterInteractive (default) - Load after page is interactive
<Script src="/analytics.js" strategy="afterInteractive" />
// lazyOnload - Load during idle time
<Script src="/widget.js" strategy="lazyOnload" />
// beforeInteractive - Load before page is interactive (use sparingly)
// Only works in app/layout.tsx or pages/_document.js
<Script src="/critical.js" strategy="beforeInteractive" />
// worker - Load in web worker (experimental)
<Script src="/heavy.js" strategy="worker" />
```
## Google Analytics
Use `@next/third-parties` instead of inline GA scripts.
```tsx
// Bad: Inline GA script
<Script src="https://www.googletagmanager.com/gtag/js?id=G-XXXXX" />
<Script id="ga-init">
{`window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'G-XXXXX');`}
</Script>
// Good: Next.js component
import { GoogleAnalytics } from '@next/third-parties/google'
export default function Layout({ children }) {
return (
<html>
<body>{children}</body>
<GoogleAnalytics gaId="G-XXXXX" />
</html>
)
}
```
## Google Tag Manager
```tsx
import { GoogleTagManager } from '@next/third-parties/google'
export default function Layout({ children }) {
return (
<html>
<GoogleTagManager gtmId="GTM-XXXXX" />
<body>{children}</body>
</html>
)
}
```
## Other Third-Party Scripts
```tsx
// YouTube embed
import { YouTubeEmbed } from '@next/third-parties/google'
<YouTubeEmbed videoid="dQw4w9WgXcQ" />
// Google Maps
import { GoogleMapsEmbed } from '@next/third-parties/google'
<GoogleMapsEmbed
apiKey="YOUR_API_KEY"
mode="place"
q="Brooklyn+Bridge,New+York,NY"
/>
```
## Quick Reference
| Pattern | Issue | Fix |
|---------|-------|-----|
| `<script src="...">` | No optimization | Use `next/script` |
| `<Script>` without id | Can't track inline scripts | Add `id` attribute |
| `<Script>` inside `<Head>` | Wrong placement | Move outside Head |
| Inline GA/GTM scripts | No optimization | Use `@next/third-parties` |
| `strategy="beforeInteractive"` outside layout | Won't work | Only use in root layout |

View File

@@ -0,0 +1,371 @@
# Self-Hosting Next.js
Deploy Next.js outside of Vercel with confidence.
## Quick Start: Standalone Output
For Docker or any containerized deployment, use standalone output:
```js
// next.config.js
module.exports = {
output: 'standalone',
};
```
This creates a minimal `standalone` folder with only production dependencies:
```
.next/
├── standalone/
│ ├── server.js # Entry point
│ ├── node_modules/ # Only production deps
│ └── .next/ # Build output
└── static/ # Must be copied separately
```
## Docker Deployment
### Dockerfile
```dockerfile
FROM node:20-alpine AS base
# Install dependencies
FROM base AS deps
WORKDIR /app
COPY package.json package-lock.json* ./
RUN npm ci
# Build
FROM base AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
RUN npm run build
# Production
FROM base AS runner
WORKDIR /app
ENV NODE_ENV=production
# Create non-root user
RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs
# Copy standalone output
COPY --from=builder /app/.next/standalone ./
COPY --from=builder /app/.next/static ./.next/static
COPY --from=builder /app/public ./public
USER nextjs
EXPOSE 3000
ENV PORT=3000
ENV HOSTNAME="0.0.0.0"
CMD ["node", "server.js"]
```
### Docker Compose
```yaml
version: '3.8'
services:
web:
build: .
ports:
- "3000:3000"
environment:
- NODE_ENV=production
restart: unless-stopped
healthcheck:
test: ["CMD", "wget", "-q", "--spider", "http://localhost:3000/api/health"]
interval: 30s
timeout: 10s
retries: 3
```
## PM2 Deployment
For traditional server deployments:
```js
// ecosystem.config.js
module.exports = {
apps: [{
name: 'nextjs',
script: '.next/standalone/server.js',
instances: 'max',
exec_mode: 'cluster',
env: {
NODE_ENV: 'production',
PORT: 3000,
},
}],
};
```
```bash
npm run build
pm2 start ecosystem.config.js
```
## ISR and Cache Handlers
### The Problem
ISR (Incremental Static Regeneration) uses filesystem caching by default. This **breaks with multiple instances**:
- Instance A regenerates page → saves to its local disk
- Instance B serves stale page → doesn't see Instance A's cache
- Load balancer sends users to random instances → inconsistent content
### Solution: Custom Cache Handler
Next.js 14+ supports custom cache handlers for shared storage:
```js
// next.config.js
module.exports = {
cacheHandler: require.resolve('./cache-handler.js'),
cacheMaxMemorySize: 0, // Disable in-memory cache
};
```
#### Redis Cache Handler Example
```js
// cache-handler.js
const Redis = require('ioredis');
const redis = new Redis(process.env.REDIS_URL);
const CACHE_PREFIX = 'nextjs:';
module.exports = class CacheHandler {
constructor(options) {
this.options = options;
}
async get(key) {
const data = await redis.get(CACHE_PREFIX + key);
if (!data) return null;
const parsed = JSON.parse(data);
return {
value: parsed.value,
lastModified: parsed.lastModified,
};
}
async set(key, data, ctx) {
const cacheData = {
value: data,
lastModified: Date.now(),
};
// Set TTL based on revalidate option
if (ctx?.revalidate) {
await redis.setex(
CACHE_PREFIX + key,
ctx.revalidate,
JSON.stringify(cacheData)
);
} else {
await redis.set(CACHE_PREFIX + key, JSON.stringify(cacheData));
}
}
async revalidateTag(tags) {
// Implement tag-based invalidation
// This requires tracking which keys have which tags
}
};
```
#### S3 Cache Handler Example
```js
// cache-handler.js
const { S3Client, GetObjectCommand, PutObjectCommand } = require('@aws-sdk/client-s3');
const s3 = new S3Client({ region: process.env.AWS_REGION });
const BUCKET = process.env.CACHE_BUCKET;
module.exports = class CacheHandler {
async get(key) {
try {
const response = await s3.send(new GetObjectCommand({
Bucket: BUCKET,
Key: `cache/${key}`,
}));
const body = await response.Body.transformToString();
return JSON.parse(body);
} catch (err) {
if (err.name === 'NoSuchKey') return null;
throw err;
}
}
async set(key, data, ctx) {
await s3.send(new PutObjectCommand({
Bucket: BUCKET,
Key: `cache/${key}`,
Body: JSON.stringify({
value: data,
lastModified: Date.now(),
}),
ContentType: 'application/json',
}));
}
};
```
## What Works vs What Needs Setup
| Feature | Single Instance | Multi-Instance | Notes |
|---------|----------------|----------------|-------|
| SSR | Yes | Yes | No special setup |
| SSG | Yes | Yes | Built at deploy time |
| ISR | Yes | Needs cache handler | Filesystem cache breaks |
| Image Optimization | Yes | Yes | CPU-intensive, consider CDN |
| Middleware | Yes | Yes | Runs on Node.js |
| Edge Runtime | Limited | Limited | Some features Node-only |
| `revalidatePath/Tag` | Yes | Needs cache handler | Must share cache |
| `next/font` | Yes | Yes | Fonts bundled at build |
| Draft Mode | Yes | Yes | Cookie-based |
## Image Optimization
Next.js Image Optimization works out of the box but is CPU-intensive.
### Option 1: Built-in (Simple)
Works automatically, but consider:
- Set `deviceSizes` and `imageSizes` in config to limit variants
- Use `minimumCacheTTL` to reduce regeneration
```js
// next.config.js
module.exports = {
images: {
minimumCacheTTL: 60 * 60 * 24, // 24 hours
deviceSizes: [640, 750, 1080, 1920], // Limit sizes
},
};
```
### Option 2: External Loader (Recommended for Scale)
Offload to Cloudinary, Imgix, or similar:
```js
// next.config.js
module.exports = {
images: {
loader: 'custom',
loaderFile: './lib/image-loader.js',
},
};
```
```js
// lib/image-loader.js
export default function cloudinaryLoader({ src, width, quality }) {
const params = ['f_auto', 'c_limit', `w_${width}`, `q_${quality || 'auto'}`];
return `https://res.cloudinary.com/demo/image/upload/${params.join(',')}${src}`;
}
```
## Environment Variables
### Build-time vs Runtime
```js
// Available at build time only (baked into bundle)
NEXT_PUBLIC_API_URL=https://api.example.com
// Available at runtime (server-side only)
DATABASE_URL=postgresql://...
API_SECRET=...
```
### Runtime Configuration
For truly dynamic config, don't use `NEXT_PUBLIC_*`. Instead:
```tsx
// app/api/config/route.ts
export async function GET() {
return Response.json({
apiUrl: process.env.API_URL,
features: process.env.FEATURES?.split(','),
});
}
```
## OpenNext: Serverless Without Vercel
[OpenNext](https://open-next.js.org/) adapts Next.js for AWS Lambda, Cloudflare Workers, etc.
```bash
npx create-sst@latest
# or
npx @opennextjs/aws build
```
Supports:
- AWS Lambda + CloudFront
- Cloudflare Workers
- Netlify Functions
- Deno Deploy
## Health Check Endpoint
Always include a health check for load balancers:
```tsx
// app/api/health/route.ts
export async function GET() {
try {
// Optional: check database connection
// await db.$queryRaw`SELECT 1`;
return Response.json({ status: 'healthy' }, { status: 200 });
} catch (error) {
return Response.json({ status: 'unhealthy' }, { status: 503 });
}
}
```
## Pre-Deployment Checklist
1. **Build locally first**: `npm run build` - catch errors before deploy
2. **Test standalone output**: `node .next/standalone/server.js`
3. **Set `output: 'standalone'`** for Docker
4. **Configure cache handler** for multi-instance ISR
5. **Set `HOSTNAME="0.0.0.0"`** for containers
6. **Copy `public/` and `.next/static/`** - not included in standalone
7. **Add health check endpoint**
8. **Test ISR revalidation** after deployment
9. **Monitor memory usage** - Node.js defaults may need tuning
## Testing Cache Handler
**Critical**: Test your cache handler on every Next.js upgrade:
```bash
# Start multiple instances
PORT=3001 node .next/standalone/server.js &
PORT=3002 node .next/standalone/server.js &
# Trigger ISR revalidation
curl http://localhost:3001/api/revalidate?path=/posts
# Verify both instances see the update
curl http://localhost:3001/posts
curl http://localhost:3002/posts
# Should return identical content
```

View File

@@ -0,0 +1,67 @@
# Suspense Boundaries
Client hooks that cause CSR bailout without Suspense boundaries.
## useSearchParams
Always requires Suspense boundary in static routes. Without it, the entire page becomes client-side rendered.
```tsx
// Bad: Entire page becomes CSR
'use client'
import { useSearchParams } from 'next/navigation'
export default function SearchBar() {
const searchParams = useSearchParams()
return <div>Query: {searchParams.get('q')}</div>
}
```
```tsx
// Good: Wrap in Suspense
import { Suspense } from 'react'
import SearchBar from './search-bar'
export default function Page() {
return (
<Suspense fallback={<div>Loading...</div>}>
<SearchBar />
</Suspense>
)
}
```
## usePathname
Requires Suspense boundary when route has dynamic parameters.
```tsx
// In dynamic route [slug]
// Bad: No Suspense
'use client'
import { usePathname } from 'next/navigation'
export function Breadcrumb() {
const pathname = usePathname()
return <nav>{pathname}</nav>
}
```
```tsx
// Good: Wrap in Suspense
<Suspense fallback={<BreadcrumbSkeleton />}>
<Breadcrumb />
</Suspense>
```
If you use `generateStaticParams`, Suspense is optional.
## Quick Reference
| Hook | Suspense Required |
|------|-------------------|
| `useSearchParams()` | Yes |
| `usePathname()` | Yes (dynamic routes) |
| `useParams()` | No |
| `useRouter()` | No |