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@koa/router

Express-style router for Koa that provides method-specific routing, URL parameters, and route-level middleware.

Since Koa 2 Spec ↗

Syntax

import Router from '@koa/router';
const router = new Router([options]);
router.get(path, ...middleware);
app.use(router.routes()).use(router.allowedMethods());

Parameters

NameTypeRequiredDescription
options object No Router options: `prefix` (string path prefix for all routes), `strict` (boolean, treat `/foo` and `/foo/` as different), `sensitive` (boolean, case-sensitive paths).

Returns

Router — A Router instance with methods for each HTTP verb.

Examples

import Koa from 'koa';
import Router from '@koa/router';

const app = new Koa();
const router = new Router();

router.get('/users', async (ctx) => {
  ctx.body = [{ id: 1, name: 'Alice' }];
});

router.get('/users/:id', async (ctx) => {
  ctx.body = { id: ctx.params.id };
});

router.post('/users', async (ctx) => {
  ctx.status = 201;
  ctx.body = { created: true };
});

app.use(router.routes());
app.use(router.allowedMethods());

app.listen(3000);
Output 
GET /users    → [{"id":1,"name":"Alice"}]
GET /users/42 → {"id":"42"}
POST /users   → 201 {"created":true}

// Nested router with prefix
const api = new Router({ prefix: '/api/v1' });

api.get('/health', async (ctx) => {
  ctx.body = { status: 'ok' };
});

app.use(api.routes());
Output 
GET /api/v1/health → {"status":"ok"}

Notes

`router.allowedMethods()` handles `OPTIONS` preflight requests and returns `405 Method Not Allowed` with an `Allow` header for routes that exist but don't support the used method. Use `router.param()` to add middleware that runs whenever a particular URL parameter is matched.

See also