@fastify/cors

CORS plugin for Fastify — configure cross-origin resource sharing with full support for preflight requests and dynamic origins.

@fastify/cors

Fastify

CORS plugin for Fastify — configure cross-origin resource sharing with full support for preflight requests and dynamic origins.

npm GitHub Docs

Fit

Bundle (gzip)

4.0 kB

15.1 kB raw

Install size includes transitive dependencies. Bundle size is gzipped browser payload.

Freshness

The Problem

Browser security blocks cross-origin requests. Configuring CORS headers in Fastify manually requires handling OPTIONS preflight responses across all routes, managing allowed origin lists, and setting correct Access-Control-* headers.

What It Does

@fastify/cors registers a plugin that intercepts all requests and adds the appropriate CORS headers. It supports static and dynamic origin configuration (function-based for per-request decisions), credentials, exposed headers, and max age for preflight caching.

Installation

bash

npm install @fastify/cors

Usage Example

typescript

import fastify from 'fastify';
import cors from '@fastify/cors';

const app = fastify();

await app.register(cors, {
  origin: (origin, cb) => {
    const allowed = ['https://myapp.com', 'https://staging.myapp.com'];
    cb(null, allowed.includes(origin ?? ''));
  },
  credentials: true,
  methods: ['GET', 'POST', 'PUT', 'DELETE'],
  allowedHeaders: ['Content-Type', 'Authorization'],
});

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