H3 is a minimal h(ttp) framework built for high performance and portability.

👉 Online Playground

✔️  Portable: Works perfectly in Serverless, Workers, and Node.js

✔️  Minimal: Small and tree-shakable

✔️  Modern: Native promise support

✔️  Extendable: Ships with a set of composable utilities but can be extended

✔️  Router: Super fast route matching using unjs/radix3

✔️  Compatible: Compatibility layer with node/connect/express middleware

# Using npm
npm install h3

# Using yarn
yarn add h3

# Using pnpm
pnpm add h3

{
  "dependencies": {
    "h3": "npm:h3-nightly@latest"
  }
}

{
  "resolutions": {
    "h3": "npm:h3-nightly@latest"
  }
}

{
  "overrides": {
    "h3": "npm:h3-nightly@latest"
  }
}

import { createServer } from "node:http";
import { createApp, eventHandler, toNodeListener } from "h3";

const app = createApp();
app.use(
  "/",
  eventHandler(() => "Hello world!"),
);

createServer(toNodeListener(app)).listen(process.env.PORT || 3000);

Example using listhen for an elegant listener:

import { createApp, eventHandler, toNodeListener } from "h3";
import { listen } from "listhen";

const app = createApp();
app.use(
  "/",
  eventHandler(() => "Hello world!"),
);

listen(toNodeListener(app));

The app instance created by h3 uses a middleware stack (see how it works) with the ability to match route prefix and apply matched middleware.

To opt-in using a more advanced and convenient routing system, we can create a router instance and register it to app instance.

import { createApp, eventHandler, createRouter } from "h3";

const app = createApp();

const router = createRouter()
  .get(
    "/",
    eventHandler(() => "Hello World!"),
  )
  .get(
    "/hello/:name",
    eventHandler((event) => `Hello ${event.context.params.name}!`),
  );

app.use(router);

Tip: We can register the same route more than once with different methods.

Routes are internally stored in a Radix Tree and matched using unjs/radix3.

For using nested routers, see this example

// Handle can directly return object or Promise<object> for JSON response
app.use(
  "/api",
  eventHandler((event) => ({ url: event.node.req.url })),
);

// We can have better matching other than quick prefix match
app.use(
  "/odd",
  eventHandler(() => "Is odd!"),
  { match: (url) => url.substr(1) % 2 },
);

// Handle can directly return string for HTML response
app.use(eventHandler(() => "<h1>Hello world!</h1>"));

// We can chain calls to .use()
app
  .use(
    "/1",
    eventHandler(() => "<h1>Hello world!</h1>"),
  )
  .use(
    "/2",
    eventHandler(() => "<h1>Goodbye!</h1>"),
  );

// We can proxy requests and rewrite cookie's domain and path
app.use(
  "/api",
  eventHandler((event) =>
    proxyRequest(event, "https://example.com", {
      // f.e. keep one domain unchanged, rewrite one domain and remove other domains
      cookieDomainRewrite: {
        "example.com": "example.com",
        "example.com": "somecompany.co.uk",
        "*": "",
      },
      cookiePathRewrite: {
        "/": "/api",
      },
    }),
  ),
);

// Legacy middleware with 3rd argument are automatically promisified
app.use(
  fromNodeMiddleware((req, res, next) => {
    req.setHeader("x-foo", "bar");
    next();
  }),
);

// Lazy loaded routes using { lazy: true }
app.use("/big", () => import("./big-handler"), { lazy: true });

H3 has a concept of composable utilities that accept event (from eventHandler((event) => {})) as their first argument. This has several performance benefits over injecting them to event or app instances in global middleware commonly used in Node.js frameworks, such as Express. This concept means only required code is evaluated and bundled, and the rest of the utilities can be tree-shaken when not used.

👉 You can check list of exported built-in utils from JSDocs Documentation.

• readRawBody(event, encoding?)
• readBody(event)
• readValidatedBody(event, validate)
• readMultipartFormData(event)

• getQuery(event)
• getValidatedQuery(event, validate)
• getRouterParams(event)
• getMethod(event, default?)
• isMethod(event, expected, allowHead?)
• assertMethod(event, expected, allowHead?)
• getRequestHeaders(event, headers) (alias: getHeaders)
• getRequestHeader(event, name) (alias: getHeader)
• getRequestURL(event)
• getRequestHost(event)
• getRequestProtocol(event)
• getRequestPath(event)
• getRequestIP(event, { xForwardedFor: boolean })

• send(event, data, type?)
• sendNoContent(event, code = 204)
• setResponseStatus(event, status)
• getResponseStatus(event)
• getResponseStatusText(event)
• getResponseHeaders(event)
• getResponseHeader(event, name)
• setResponseHeaders(event, headers) (alias: setHeaders)
• setResponseHeader(event, name, value) (alias: setHeader)
• appendResponseHeaders(event, headers) (alias: appendHeaders)
• appendResponseHeader(event, name, value) (alias: appendHeader)
• defaultContentType(event, type)
• sendRedirect(event, location, code=302)
• isStream(data)
• sendStream(event, data)
• writeEarlyHints(event, links, callback)

• sanitizeStatusMessage(statusMessage)
• sanitizeStatusCode(statusCode, default = 200)

• sendError(event, error, debug?)
• createError({ statusCode, statusMessage, data? })

• useBase(base, handler)

• sendProxy(event, { target, ...options })
• proxyRequest(event, { target, ...options })
• fetchWithEvent(event, req, init, { fetch? }?)
• getProxyRequestHeaders(event)

• parseCookies(event)
• getCookie(event, name)
• setCookie(event, name, value, opts?)
• deleteCookie(event, name, opts?)
• splitCookiesString(cookiesString)

• useSession(event, config = { password, maxAge?, name?, cookie?, seal?, crypto? })
• getSession(event, config)
• updateSession(event, config, update)
• sealSession(event, config)
• unsealSession(event, config, sealed)
• clearSession(event, config)

• handleCacheHeaders(event, opts)

• handleCors(options) (see h3-cors for more detail about options)
• isPreflightRequest(event)
• isCorsOriginAllowed(event)
• appendCorsHeaders(event, options) (see h3-cors for more detail about options)
• appendCorsPreflightHeaders(event, options) (see h3-cors for more detail about options)

You can use more H3 event utilities made by the community.

Please check their READMEs for more details.

PRs are welcome to add your packages.

• h3-typebox
  • validateBody(event, schema)
  • validateQuery(event, schema)
• h3-zod
  • useValidatedBody(event, schema)
  • useValidatedQuery(event, schema)
• h3-valibot
  • useValidateBody(event, schema)
  • useValidateParams(event, schema)

MIT