---
name: nextjs-best-practices
description: "Next.js App Router principles. Server Components, data fetching, routing patterns."
allowed-tools: Read, Write, Edit, Glob, Grep
risk: unknown
source: community
---
# Next.js Best Practices
> Principles for Next.js App Router development.
---
## 1. Server vs Client Components
### Decision Tree
```
Does it need...?
│
├── useState, useEffect, event handlers
│ └── Client Component ('use client')
│
├── Direct data fetching, no interactivity
│ └── Server Component (default)
│
└── Both?
└── Split: Server parent + Client child
```
### By Default
| Type | Use |
|------|-----|
| **Server** | Data fetching, layout, static content |
| **Client** | Forms, buttons, interactive UI |
---
## 2. Data Fetching Patterns
### Fetch Strategy
| Pattern | Use |
|---------|-----|
| **Default** | Static (cached at build) |
| **Revalidate** | ISR (time-based refresh) |
| **No-store** | Dynamic (every request) |
### Data Flow
| Source | Pattern |
|--------|---------|
| Database | Server Component fetch |
| API | fetch with caching |
| User input | Client state + server action |
---
## 3. Routing Principles
### File Conventions
| File | Purpose |
|------|---------|
| `page.tsx` | Route UI |
| `layout.tsx` | Shared layout |
| `loading.tsx` | Loading state |
| `error.tsx` | Error boundary |
| `not-found.tsx` | 404 page |
### Route Organization
| Pattern | Use |
|---------|-----|
| Route groups `(name)` | Organize without URL |
| Parallel routes `@slot` | Multiple same-level pages |
| Intercepting `(.)` | Modal overlays |
---
## 4. API Routes
### Route Handlers
| Method | Use |
|--------|-----|
| GET | Read data |
| POST | Create data |
| PUT/PATCH | Update data |
| DELETE | Remove data |
### Best Practices
- Validate input with Zod
- Return proper status codes
- Handle errors gracefully
- Use Edge runtime when possible
---
## 5. Performance Principles
### Image Optimization
- Use next/image component
- Set priority for above-fold
- Provide blur placeholder
- Use responsive sizes
### Bundle Optimization
- Dynamic imports for heavy components
- Route-based code splitting (automatic)
- Analyze with bundle analyzer
---
## 6. Metadata
### Static vs Dynamic
| Type | Use |
|------|-----|
| Static export | Fixed metadata |
| generateMetadata | Dynamic per-route |
### Essential Tags
- title (50-60 chars)
- description (150-160 chars)
- Open Graph images
- Canonical URL
---
## 7. Caching Strategy
### Cache Layers
| Layer | Control |
|-------|---------|
| Request | fetch options |
| Data | revalidate/tags |
| Full route | route config |
### Revalidation
| Method | Use |
|--------|-----|
| Time-based | `revalidate: 60` |
| On-demand | `revalidatePath/Tag` |
| No cache | `no-store` |
---
## 8. Server Actions
### Use Cases
- Form submissions
- Data mutations
- Revalidation triggers
### Best Practices
- Mark with 'use server'
- Validate all inputs
- Return typed responses
- Handle errors
---
## 9. Anti-Patterns
| ❌ Don't | ✅ Do |
|----------|-------|
| 'use client' everywhere | Server by default |
| Fetch in client components | Fetch in server |
| Skip loading states | Use loading.tsx |
| Ignore error boundaries | Use error.tsx |
| Large client bundles | Dynamic imports |
---
## 10. Project Structure
```
app/
├── (marketing)/ # Route group
│ └── page.tsx
├── (dashboard)/
│ ├── layout.tsx # Dashboard layout
│ └── page.tsx
├── api/
│ └── [resource]/
│ └── route.ts
└── components/
└── ui/
```
---
> **Remember:** Server Components are the default for a reason. Start there, add client only when needed.
## When to Use
This skill is applicable to execute the workflow or actions described in the overview.