Registry / web-framework / koa
library0.3jsnpmunverified

Koa is an expressive HTTP middleware framework for Node.js, designed to build web applications and APIs. It emphasizes a small core, relying on its middleware stack for functionality, and does not bundle any middleware. The current stable version is 3.2.0, with active development across both v2 and v3 branches, indicating a continuous release cadence.

npm install koa
INSTALL
IMPORT
SIG · KOA
K
koa
web-frameworkjavascriptv0.3
Install
Import
Disk
Pass rate
0/ 6
Env Coverage0 / 6
glibc
1822
musl
1822
Install & Compatibility
Where this runs
tested against v? · npm install
Install × environment matrix
Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux
musl
node 18226 runs
build_error
glibc
node 18226 runs
build_error
Code
Verified usage

Verified import paths — ran on the pinned version, not inferred.

Koa
import Koa from 'koa';
const Koa = require('koa');
While Koa is published as CommonJS and `require` still works, `import` is generally recommended for new projects targeting Node.js v18+.

A basic Koa server that listens on port 3000 and responds with 'Hello Koa' to all requests.

import Koa from 'koa'; const app = new Koa(); // response app.use(ctx => { ctx.body = 'Hello Koa'; }); app.listen(3000, () => { console.log('Koa server listening on port 3000'); });
koa --version
Debug
Known issues
breakingKoa v3 removed support for the deprecated v1.x middleware signature. Middleware functions must now be `async` functions or return `Promise`s.
fix
Update old middleware to use `async (ctx, next) => { await next(); }` syntax, or return a Promise from `next()`.
affects: >=3.0.0
gotchaKoa provides a minimal core and does not bundle any middleware. Essential functionalities like routing, body parsing, or sessions must be added via separate middleware packages.
fix
Install necessary middleware packages (e.g., `koa-router`, `koa-body`) and register them using `app.use()`.
affects: >=1.0.0
breakingKoa requires Node.js v18.0.0 or higher due to its reliance on ES2015 features and async/await support.
fix
Ensure your development and production environments are running Node.js v18.0.0 or a newer compatible version.
affects: >=3.0.0
gotchaVersions of Koa prior to v2.16.4 and specific earlier v3.x releases contained a Host Header Injection vulnerability via `ctx.hostname` (GHSA-7gcc-r8m5-44qm).
fix
Upgrade to Koa v2.16.4+ or the latest v3.x version to ensure security patches are applied.
affects: <2.16.4, <3.0.0 (and specific earlier v3 patches)
Errors
Common errors & fixes
SyntaxError: await is only valid in async functions and the top level bodies of modules
Attempting to use `await` within a Koa middleware function that is not declared as `async`.
fix
Declare your middleware function as `async`, e.g., `app.use(async (ctx, next) => { await next(); });`.
Error: next() cannot be called more than once
A Koa middleware function is invoking `next()` multiple times, or not awaiting it correctly, leading to re-entrancy issues.
fix
Ensure `await next();` is called exactly once within each middleware. Review error handling logic or early exits that might bypass `await next()`.
TypeError: ctx.render is not a function
Attempting to use a feature like template rendering (e.g., `ctx.render`) without installing and registering the corresponding Koa middleware.
fix
Install the necessary Koa-compatible middleware package (e.g., `koa-views` for template rendering) and register it with `app.use()`.
ERR_HTTP_HEADERS_SENT: Cannot set headers after they are sent to the client
Attempting to modify HTTP headers or send response content after the response has already been partially or fully sent to the client.
fix
Ensure that `ctx.set()` or `ctx.body = ...` operations occur before any part of the response has been flushed. This often happens if `await next()` is omitted or if asynchronous operations continue after the response is sent.
Upgrade
Version history
0.3latest on npm
Audit
Dependencies

No dependency data recorded yet.

Agent activity
4 hits · last 30 days
node
4
Resources
koa — npm install koa · libregistry