µExpress / Ultimate Express

The Ultimate Express. Fastest http server with full Express compatibility, based on µWebSockets.

This library is a very fast re-implementation of Express.js 4. It is designed to be a drop-in replacement for Express.js, with the same API and functionality, while being much faster. It is not a fork of Express.js.
To make sure µExpress matches behavior of Express in all cases, we run all tests with Express first, and then with µExpress and compare results to make sure they match.

npm install ultimate-express -> replace express with ultimate-express -> done*

Similar projects based on uWebSockets:

• express on Bun - since Bun uses uWS for its HTTP module, Express is about 2-3 times faster than on Node.js, but still almost 2 times slower than µExpress because it doesn't do uWS-specific optimizations.
• hyper-express - while having a similar API to Express, it's very far from being a drop-in replacement, and implements most of the functionality differently. This creates a lot of random quirks and issues, making the switch quite difficult. Built in middlewares are also very different, middlewares for Express are mostly not supported.
• uwebsockets-express - this library is closer to being a drop-in replacement, but misses a lot of APIs, depends on Express by calling it's methods under the hood and doesn't try to optimize routing by using native uWS router.

Tested using wrk (-d 60 -t 1 -c 200). Etag was disabled in both Express and µExpress. Tested on Ubuntu 22.04, Node.js 20.17.0, AMD Ryzen 5 3600, 64GB RAM.

Tested using bun-http-framework-benchmark. This table only includes Node.js results. For full table with other runtimes, check here.

Also tested on a real-world application with templates, static files and dynamic pages with data from database, and showed 1.5-4X speedup in requests per second depending on the page.

In a lot of cases, you can just replace require("express") with require("ultimate-express") and everything works the same. But there are some differences:

• case sensitive routing is enabled by default.
• a new option catch async errors is added. If it's enabled, you don't need to use express-async-errors module.
• request body is only read for POST, PUT and PATCH requests by default. You can add additional methods by setting body methods to array with uppercased methods.
• For HTTPS, instead of doing this:

const https = require("https");
const express = require("express");

const app = express();

https.createServer({
    key: fs.readFileSync('path/to/key.pem'),
    cert: fs.readFileSync('path/to/cert.pem')
}, app).listen(3000, () => {
    console.log('Server is running on port 3000');
});

You have to pass uwsOptions to the express() constructor:

const express = require("ultimate-express");

const app = express({
    uwsOptions: {
        // https://unetworking.github.io/uWebSockets.js/generated/interfaces/AppOptions.html
        key_file_name: 'path/to/key.pem',
        cert_file_name: 'path/to/cert.pem'
    }
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

• This also applies to non-SSL HTTP too. Do not create http server manually, use app.listen() instead.

1. µExpress tries to optimize routing as much as possible, but it's only possible if:

• case sensitive routing is enabled (it is by default, unlike in normal Express).
• only string paths without regex characters like *, +, (), {}, etc. can be optimized.
• only 1-level deep routers can be optimized.

Optimized routes can be up to 10 times faster than normal routes, as they're using native uWS router and have pre-calculated path.

2. Do not use external serve-static module. Instead use built-in express.static() middleware, which is optimized for uExpress.

3. Do not use body-parser module. Instead use built-in express.text(), express.json() etc.

4. Do not set body methods to read body of requests with GET method or other methods that don't need a body. Reading body makes endpoint about 15% slower.

5. By default, µExpress creates 1 (or 0 if your CPU has only 1 core) child thread to improve performance of reading files. You can change this number by setting threads to a different number in express(), or set to 0 to disable thread pool (express({ threads: 0 })). Threads are shared between all express() instances, with largest threads number being used. Using more threads will not necessarily improve performance. Sometimes not using threads at all is faster, please test both options.

6. Don't read req.connection.remoteAddress (or req.ip if trust proxy is disabled) after response is finished. In general, reading IP in uWS is quite slow (~15% slower), and you should only read it when you need it while request is still open. If you'll read it after response, it'll make µExpress read IP for every single request after, even when it's not needed.

Since you don't create http server manually, you can't properly use http.on("upgrade") to handle WebSockets. To solve this, there's currently 2 options:

• There's a sister library that implements ws compatible API: Ultimate WS. It's same concept as this library, but for WebSockets: fast drop-in replacement for ws module with support for Ultimate Express upgrades. There's a guide for how to upgrade http requests in the documentation.
• You can simply use app.uwsApp to access uWebSockets.js App instance and call its ws() method directly.

In general, basically all features and options are supported. Use Express 4.x documentation for API reference.

✅ - Full support (all features and options are supported)
🚧 - Partial support (some options are not supported)
❌ - Not supported

• ✅ express()
• ✅ express.Router()
• ✅ express.json()
• ✅ express.urlencoded()
• ✅ express.static()
• ✅ express.text()
• ✅ express.raw()
• 🚧 express.request (this is not a constructor but a prototype for replacing methods)
• 🚧 express.response (this is not a constructor but a prototype for replacing methods)

• ✅ app.listen(port[, host][, callback])
• ✅ app.listen(unix_socket[, callback])
• ✅ app.METHOD() (app.get, app.post, etc.)
• ✅ app.route()
• ✅ app.all()
• ✅ app.use()
• ✅ app.mountpath
• ✅ app.set()
• ✅ app.get()
• ✅ app.enable()
• ✅ app.disable()
• ✅ app.enabled()
• ✅ app.disabled()
• ✅ app.path()
• ✅ app.param(name, callback)
• ✅ app.param(callback)
• ✅ app.engine()
• ✅ app.render()
• ✅ app.locals
• ✅ app.settings
• ✅ app.engines
• ✅ app.on("mount")
• ✅ HEAD method

• ✅ case sensitive routing
• ✅ env
• ✅ etag
• ✅ jsonp callback name
• ✅ json escape
• ✅ json replacer
• ✅ json spaces
• ✅ query parser
• ✅ strict routing
• ✅ subdomain offset
• ✅ trust proxy
• ✅ views
• ✅ view cache
• ✅ view engine
• ✅ x-powered-by

• ✅ implements Readable stream
• ✅ req.app
• ✅ req.baseUrl
• ✅ req.body
• ✅ req.cookies
• ✅ req.fresh
• ✅ req.hostname
• ✅ req.headers
• ✅ req.headersDistinct
• ✅ req.rawHeaders
• ✅ req.ip
• ✅ req.ips
• ✅ req.method
• ✅ req.url
• ✅ req.originalUrl
• ✅ req.params
• ✅ req.path
• ✅ req.protocol
• ✅ req.query
• ✅ req.res
• ✅ req.secure
• ✅ req.signedCookies
• ✅ req.stale
• ✅ req.subdomains
• ✅ req.xhr
• 🚧 req.route (route implementation is different from Express)
• 🚧 req.connection, req.socket (only encrypted, remoteAddress, localPort and remotePort are supported)
• ✅ req.accepts()
• ✅ req.acceptsCharsets()
• ✅ req.acceptsEncodings()
• ✅ req.acceptsLanguages()
• ✅ req.get()
• ✅ req.is()
• ✅ req.param()
• ✅ req.range()

• ✅ implements Writable stream
• ✅ res.app
• ✅ res.headersSent
• ✅ res.req
• ✅ res.locals
• ✅ res.append()
• ✅ res.attachment()
• ✅ res.cookie()
• ✅ res.clearCookie()
• ✅ res.download()
• ✅ res.end()
• ✅ res.format()
• ✅ res.getHeader(), res.get()
• ✅ res.json()
• ✅ res.jsonp()
• ✅ res.links()
• ✅ res.location()
• ✅ res.redirect()
• ✅ res.render()
• ✅ res.send()
• ✅ res.sendFile()
• • ✅ options.maxAge
• • ✅ options.root
• • ✅ options.lastModified
• • ✅ options.headers
• • ✅ options.dotfiles
• • ✅ options.acceptRanges
• • ✅ options.cacheControl
• • ✅ options.immutable
• • ✅ Range header
• • ✅ Setting ETag header
• • ✅ If-Match header
• • ✅ If-Modified-Since header
• • ✅ If-Unmodified-Since header
• • ✅ If-Range header
• ✅ res.sendStatus()
• ✅ res.header(), res.setHeader(), res.set()
• ✅ res.status()
• ✅ res.type()
• ✅ res.vary()
• ✅ res.removeHeader()
• ✅ res.write()
• ✅ res.writeHead()

• ✅ router.all()
• ✅ router.METHOD() (router.get, router.post, etc.)
• ✅ router.route()
• ✅ router.use()
• ✅ router.param(name, callback)
• ✅ router.param(callback)
• ✅ options.caseSensitive
• ✅ options.strict
• ✅ options.mergeParams

Almost all middlewares that are compatible with Express are compatible with µExpress. Here's list of middlewares that we test for compatibility:

• ✅ body-parser (use express.text() etc instead for better performance)
• ✅ cookie-parser
• ✅ cookie-session
• ✅ serve-static (use express.static() instead for better performance)
• ✅ serve-index
• ✅ cors
• ✅ errorhandler
• ✅ method-override
• ✅ multer
• ✅ response-time
• ✅ express-fileupload
• ✅ express-session
• ✅ express-rate-limit
• ✅ express-subdomain
• ✅ vhost

Middlewares and modules that are confirmed to not work:

• ❌ compression - doesn't error, but doesn't compress
• ❌ express-async-errors - doesn't work, use app.set('catch async errors', true) instead.

Any Express view engine should work. Here's list of engines we include in our test suite:

• ✅ ejs
• ✅ pug
• ✅ express-dot-engine
• ✅ express-art-template
• ✅ express-handlebars
• ✅ swig