nextjs-best-practices

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	Version/config dependent; current fetch defaults are uncached
Explicit cache	fetch(url, { cache: "force-cache" }) when data may be shared
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
• Choose Node.js or Edge runtime according to dependency and deployment support; do not assume Node APIs are available on Edge

---

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'
• Authenticate and authorize each action/handler on the server; exported actions are callable endpoints
• 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.

Version scope

Check the installed Next.js version and whether Cache Components is enabled before applying caching advice. The official caching guide distinguishes these models. Test freshness and invalidation explicitly; never put user-specific secrets or authorization-dependent responses into a shared cache.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.