Netlify Development Best Practices

Overview

This skill provides comprehensive guidelines for building and deploying projects on Netlify, covering serverless functions, edge functions, background functions, scheduled functions, Netlify Blobs, Image CDN, and deployment configuration.

Core Principles

Use in-code configuration via exported
```
config
```
objects (preferred over netlify.toml)
Never add version numbers to imported Netlify packages
Only add CORS headers when explicitly required
Leverage appropriate function types for different use cases
Use Netlify Blobs for state and data storage

Function Types Overview

Type	Use Case	Timeout	Path Convention
Serverless	Standard API endpoints	10s (26s Pro)	`/.netlify/functions/name`
Edge	Request/response modification	50ms CPU	Custom paths
Background	Long-running async tasks	15 minutes	`-background` suffix
Scheduled	Cron-based tasks	10s (26s Pro)	Configured schedule

Serverless Functions

Basic Structure

typescript

// netlify/functions/hello.mts
import type { Context } from '@netlify/functions';

export default async (request: Request, context: Context) => {
  try {
    // Validate request
    if (request.method !== 'POST') {
      return new Response('Method Not Allowed', { status: 405 });
    }

    const body = await request.json();

    // Business logic
    const result = await processData(body);

    return Response.json(result);
  } catch (error) {
    console.error('Function error:', error);
    return Response.json({ error: 'Internal Server Error' }, { status: 500 });
  }
};

export const config = {
  path: '/api/hello',
};

Configuration Options

typescript

export const config = {
  // Custom path (instead of /.netlify/functions/name)
  path: '/api/users',

  // HTTP methods (optional, allows all by default)
  method: ['GET', 'POST'],

  // Rate limiting
  rateLimit: {
    windowSize: 60,
    windowLimit: 100,
  },
};

Path Conventions

Default path:
```
/.netlify/functions/{function_name}
```
Custom paths via config completely replace the default
Use custom paths for cleaner API URLs

Edge Functions

Use Cases

Modify requests before they reach the origin
Modify responses before returning to users
Geolocation-based personalization
A/B testing
Authentication at the edge

Implementation

typescript

// netlify/edge-functions/geo-redirect.ts
import type { Context } from '@netlify/edge-functions';

export default async (request: Request, context: Context) => {
  const country = context.geo.country?.code || 'US';

  // Redirect based on country
  if (country === 'DE') {
    return Response.redirect(new URL('/de', request.url));
  }

  // Continue to origin
  return context.next();
};

export const config = {
  path: '/*',
  excludedPath: ['/api/*', '/_next/*'],
};

Response Modification

typescript

export default async (request: Request, context: Context) => {
  // Get response from origin
  const response = await context.next();

  // Modify headers
  response.headers.set('X-Custom-Header', 'value');

  // Transform HTML
  const html = await response.text();
  const modifiedHtml = html.replace('</body>', '<script>...</script></body>');

  return new Response(modifiedHtml, {
    status: response.status,
    headers: response.headers,
  });
};

Background Functions

Key Characteristics

15-minute timeout (wall clock time)
Immediately return 202 status code
Return values are ignored
Must have
```
-background
```
suffix

Implementation

typescript

// netlify/functions/process-video-background.mts
import type { Context } from '@netlify/functions';
import { getStore } from '@netlify/blobs';

export default async (request: Request, context: Context) => {
  const { videoId } = await request.json();

  // Long-running processing
  const result = await processVideo(videoId);

  // Store result for later retrieval
  const store = getStore('processed-videos');
  await store.setJSON(videoId, result);

  // Return value is ignored
  return new Response('Processing complete');
};

export const config = {
  path: '/api/process-video',
};

Retrieving Background Results

typescript

// netlify/functions/get-video-status.mts
import { getStore } from '@netlify/blobs';

export default async (request: Request, context: Context) => {
  const url = new URL(request.url);
  const videoId = url.searchParams.get('id');

  const store = getStore('processed-videos');
  const result = await store.get(videoId, { type: 'json' });

  if (!result) {
    return Response.json({ status: 'processing' });
  }

  return Response.json({ status: 'complete', data: result });
};

Scheduled Functions

Configuration

typescript

// netlify/functions/daily-cleanup.mts
import type { Context } from '@netlify/functions';

export default async (request: Request, context: Context) => {
  console.log('Running daily cleanup...');

  // Cleanup logic
  await cleanupOldRecords();

  return new Response('Cleanup complete');
};

export const config = {
  schedule: '@daily', // or '0 0 * * *' for midnight UTC
};

Schedule Patterns

typescript

// Common patterns
export const config = {
  schedule: '@hourly',     // Every hour
  schedule: '@daily',      // Every day at midnight
  schedule: '@weekly',     // Every week
  schedule: '*/15 * * * *', // Every 15 minutes
  schedule: '0 9 * * 1-5',  // 9 AM on weekdays
};

Netlify Blobs

Basic Usage

typescript

import { getStore } from '@netlify/blobs';

// Get a store
const store = getStore('my-store');

// Store data
await store.set('key', 'string value');
await store.setJSON('json-key', { foo: 'bar' });

// Retrieve data
const value = await store.get('key');
const jsonValue = await store.get('json-key', { type: 'json' });

// Delete data
await store.delete('key');

// List keys
const { blobs } = await store.list();

Binary Data

typescript

import { getStore } from '@netlify/blobs';

const store = getStore('files');

// Store binary data
const arrayBuffer = await file.arrayBuffer();
await store.set('uploads/file.pdf', arrayBuffer, {
  metadata: { contentType: 'application/pdf' },
});

// Retrieve binary data
const blob = await store.get('uploads/file.pdf', { type: 'blob' });

Deploy-specific vs Site-wide

typescript

// Site-wide store (persists across deploys)
const siteStore = getStore({
  name: 'user-data',
  siteID: context.site.id,
});

// Deploy-specific store (scoped to deployment)
const deployStore = getStore({
  name: 'cache',
  deployID: context.deploy.id,
});

Netlify Image CDN

Usage

html

<!-- Basic optimization -->
<img src="/.netlify/images?url=/images/hero.jpg&w=800&q=80" alt="Hero">

<!-- With fit and format -->
<img src="/.netlify/images?url=/images/hero.jpg&w=400&h=300&fit=cover&fm=webp" alt="Hero">

Parameters

```
url
```
: Source image path (required)
```
w
```
: Width in pixels
```
h
```
: Height in pixels
```
q
```
: Quality (1-100)
```
fit
```
: cover, contain, fill
```
fm
```
: Format (webp, avif, auto)

Programmatic Usage

typescript

function getOptimizedImageUrl(src: string, options: ImageOptions) {
  const params = new URLSearchParams({
    url: src,
    w: String(options.width),
    q: String(options.quality || 80),
    fm: 'auto',
  });

  return `/.netlify/images?${params}`;
}

Environment Variables

Access in Functions

typescript

export default async (request: Request, context: Context) => {
  // Access environment variables
  const apiKey = Netlify.env.get('API_KEY');
  const dbUrl = process.env.DATABASE_URL;

  if (!apiKey) {
    console.error('API_KEY not configured');
    return Response.json({ error: 'Configuration error' }, { status: 500 });
  }

  // Use variables
};

Context Variables

typescript

export default async (request: Request, context: Context) => {
  // Available context
  const { site, deploy, geo, ip, requestId } = context;

  console.log('Site ID:', site.id);
  console.log('Deploy ID:', deploy.id);
  console.log('Country:', geo.country?.code);
  console.log('Request ID:', requestId);
};

Build Configuration

netlify.toml

toml

[build]
  command = "npm run build"
  publish = "dist"
  functions = "netlify/functions"

[build.environment]
  NODE_VERSION = "20"

[[redirects]]
  from = "/api/*"
  to = "/.netlify/functions/:splat"
  status = 200

[[headers]]
  for = "/*"
  [headers.values]
    X-Frame-Options = "DENY"
    X-Content-Type-Options = "nosniff"

[functions]
  node_bundler = "esbuild"

[dev]
  command = "npm run dev"
  port = 3000
  targetPort = 5173

File-based Uploads

Direct Upload to Functions

typescript

// netlify/functions/upload.mts
import { getStore } from '@netlify/blobs';

export default async (request: Request, context: Context) => {
  const formData = await request.formData();
  const file = formData.get('file') as File;

  if (!file) {
    return Response.json({ error: 'No file provided' }, { status: 400 });
  }

  const store = getStore('uploads');
  const key = `${Date.now()}-${file.name}`;

  await store.set(key, await file.arrayBuffer(), {
    metadata: {
      contentType: file.type,
      originalName: file.name,
    },
  });

  return Response.json({ key, message: 'Upload successful' });
};

Site Management

Creating and Linking Sites

bash

# Initialize new site
netlify init

# Link existing site
netlify link

# Deploy manually
netlify deploy

# Deploy to production
netlify deploy --prod

Local Development

Netlify Dev

bash

# Start local development server
netlify dev

# With specific port
netlify dev --port 8888

# With live reload
netlify dev --live

Testing Functions Locally

bash

# Invoke function directly
netlify functions:invoke hello --payload '{"name": "World"}'

# Serve functions only
netlify functions:serve

Error Handling Best Practices

Structured Error Responses

typescript

interface ErrorResponse {
  error: string;
  code: string;
  details?: unknown;
}

function errorResponse(status: number, error: ErrorResponse): Response {
  return Response.json(error, { status });
}

export default async (request: Request, context: Context) => {
  try {
    // Validation
    const body = await request.json();
    if (!body.email) {
      return errorResponse(400, {
        error: 'Email is required',
        code: 'MISSING_EMAIL',
      });
    }

    // Business logic
    const result = await processRequest(body);
    return Response.json(result);

  } catch (error) {
    console.error('Function error:', error);
    return errorResponse(500, {
      error: 'Internal server error',
      code: 'INTERNAL_ERROR',
    });
  }
};

Security Guidelines

Input Validation

typescript

import { z } from 'zod';

const RequestSchema = z.object({
  email: z.string().email(),
  name: z.string().min(1).max(100),
});

export default async (request: Request, context: Context) => {
  const body = await request.json();

  const result = RequestSchema.safeParse(body);
  if (!result.success) {
    return Response.json(
      { error: 'Validation failed', details: result.error.issues },
      { status: 400 }
    );
  }

  // Use validated data
  const { email, name } = result.data;
};

Authentication

typescript

async function verifyToken(request: Request): Promise<User | null> {
  const auth = request.headers.get('Authorization');
  if (!auth?.startsWith('Bearer ')) {
    return null;
  }

  const token = auth.slice(7);
  // Verify token logic
  return verifyJWT(token);
}

export default async (request: Request, context: Context) => {
  const user = await verifyToken(request);
  if (!user) {
    return Response.json({ error: 'Unauthorized' }, { status: 401 });
  }

  // Authenticated request handling
};

Common Pitfalls to Avoid

Adding version numbers to
```
@netlify/functions
```
imports
Adding CORS headers when not explicitly needed
Using wrong function type for the use case
Forgetting
```
-background
```
suffix for background functions
Not using Blobs for persistent storage in background functions
Ignoring the 15-minute timeout for background functions
Not validating input in serverless functions
Hardcoding environment variables
Not handling errors appropriately at the edge
Using serverless functions for tasks better suited to edge functions

netlify-development

NPX Install

Tags

SKILL.md Content

Netlify Development Best Practices

Overview

Core Principles

Function Types Overview

Serverless Functions

Basic Structure

Configuration Options

Path Conventions

Edge Functions

Use Cases

Implementation

Response Modification

Background Functions

Key Characteristics

Implementation

Retrieving Background Results

Scheduled Functions

Configuration

Schedule Patterns

Netlify Blobs

Basic Usage

Binary Data

Deploy-specific vs Site-wide

Netlify Image CDN

Usage

Parameters

Programmatic Usage

Environment Variables

Access in Functions

Context Variables

Build Configuration

netlify.toml

File-based Uploads

Direct Upload to Functions

Site Management

Creating and Linking Sites

Local Development

Netlify Dev

Testing Functions Locally

Error Handling Best Practices

Structured Error Responses

Security Guidelines

Input Validation

Authentication

Common Pitfalls to Avoid