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Deno 1.35

Deno 1.35: A fast and convenient way to build web servers

Deno’s vision is to make programming as simple as possible, which is why the runtime ships with a robust toolchain, native TypeScript support, and web standard APIs, so you can skip configuration and learning a new set of APIs and be productive immediately.

Today’s minor release brings us closer to that vision:

Besides the aforementioned features, this release also includes many other improvements and bug fixes:

Deno.serve() is now stable

The long awaited new web server API, Deno.serve(), is now stable. It offers a much easier API while significantly enhancing performance.

Deno.serve() allows developers to set up a web server using a single line of code:

Deno.serve((req) => new Response("hello world"));

Contrast it with earlier API, Deno.serveHttp(), which required the setup of an async iterator over connections and subsequent handling of HTTP events (in an async IIFE):

async function handleHttp(conn: Deno.Conn) {
  (async () => {
    for await (const r of Deno.serveHttp(conn)) {
      r.respondWith(new Response("Hello World"));

for await (const conn of Deno.listen({ port: 8000 })) {

Deno.serve() uses web standard Request and Response objects, for seamless interaction with fetch(), web streams, and other standard APIs.

Moreover, Deno.serve() delivers tangible performance benefits. In our benchmarks, a hello-world server built with Deno.serve() yielded twice the throughput of a similar Node.js server, with better tail latency and more efficient memory use.

Deno 1.35.0 vs Node 18.12.1 HTTP performance

Any npm package using node:http module will use this API under the hood to enjoy the same performance benefits. Here’s a comparison of running a “hello-world” express server in Node.js and Deno:

Deno 1.35.0 vs Node 18.12.1 express performance

These benchmarks were made against Node 18.12.1 on a bare metal Intel Xeon E-2378G at 2.80Ghz, running Ubuntu 22.04.

For more information on this new API, refer to the Deno.serve() documentation and the Deno manual.

Improvements to npm and Node compatibility

Deno’s npm compatibility allows you to use your go-to packages with minimal supply chain risks.

This month we made great improvements to compatibility of http, https and zlib modules. Full list of changes to built-in Node.js module includes:

  • fs.FileHandle
  • http.ClientRequest.upgrade
  • http.IncomingMessageForClient.complete
  • http2
  • https.createServer
  • process.reallyExit
  • v8.setFlagsFromString
  • zlib.brotliCompress
  • zlib.brotliCompressSync
  • zlib.brotliDecompress
  • zlib.brotliDecompressSync
  • zlib.createBrotliCompress
  • zlib.createBrotliDecompress

Every release adds support for more and more npm packages. Here’s a list of highly anticipated packages, that now work with Deno thanks to the improvements to previously mentioned APIs:

Next month, we will focus our efforts on getting @grpc/grpc-js, google-cloud-node and various DB drivers working. If you find a package that doesn’t work, please report an issue at denoland/deno repo.

Deno API changes

Following APIs were added to the Deno namespace:

  • Deno.AtomicOperation
  • Deno.errors.FilesystemLoop
  • Deno.errors.IsADirectory
  • Deno.errors.NetworkUnreachable
  • Deno.errors.NotADirectory
  • Deno.InspectOptions.breakLength
  • Deno.InspectOptions.escapeSequences
  • Deno.KV.enqueue

Additionally these APIs no longer require --unstable flag:

  • Deno.ConnectTlsOptions.alpnProtocols
  • Deno.ListenTlsOptions.alpnProtocols
  • Deno.serve
  • Deno.StartTlsOptions.alpnProtocols

You can learn more about these APIs, by visiting the API reference.

Web API changes

This release brings support for Headers.getSetCookie() and ReadableStream.from() APIs, while URLSearchParams.delete() and URLSearchParams.has() now support value parameter.

Language server improvements

This release brings a huge quality of life improvement to the LSP, by fixing a long standing problem with auto-imports for npm packages and import maps.

Auto-complete for npm: specifiers works now:

So does auto-complete for import map specifiers:

Changes to the standard library

Rewrite of semver

In this release, semver module of the standard library has been rewritten from scratch to reduce the internal complexity and clean up the public interfaces. The module started as a port of npm:semver, but it had a lot of undesired characteristics such as; stateful SemVer class or excessively overloaded APIs.

In this release each semver instance becomes an immutable plain JavaScript object. Most APIs now only accept single set of input types. The old interfaces are supported with @deprecated JSDoc tags. That way your editor will point out that they need to be updated. Old interfaces are scheduled to be removed in std@0.200.0.

import { lte, parse } from "";

lte(parse("1.2.3"), parse("1.2.4"));

lte("1.2.3", "1.2.4"); // This is deprecated now

Thank you to Justin Chase, Jesse Jackson, Max Duval, Asher Gomez, Tim Reichen for contributing this change.

Addition of html/entities

In this release, the new standard module html has been added. The module currently has escape and unescape APIs, which escapes/unescapes the special HTML characters in the given strings.

import {
} from "`";

escape("<html>"); // => "&lt;html&gt;"
unescape("&lt;html&gt;"); // =>  "<html>"

escape escapes 5 characters, &, <, >, ", and ', by default. unescape handles those 5 plus &apos;, &nbsp;, and decimal and hex HTML entities by default. There’s also an option for enabling the handling of all known HTML entities. See the module docs for more details.

Thanks to Lionel Rowe for contributing this feature.

Addition of http/user_agent

In this release http/user_agent has been added. The module detects the OS, CPU, device, and browser types from the given user agent string. The module is heavily inspired by npm:ua-parser-js.

import { UserAgent } from "";

const ua = new UserAgent(
  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36",

console.log(ua.os); // => { name: "Linux", version: "x86_64" }
console.log(ua.cpu); // => { architecture: "amd64" }
console.log(ua.engine); // => { name: "Blink", version: "51.0.2704.103" }
console.log(ua.browser); // => { name: "Chrome", version: "51.0.2704.103", major: "51" }

Thanks to Kitson Kelly for contributing this feature.

V8 11.6 and TypeScript 5.1.6

Finally, Deno v1.35 ships with V8 11.6 and TypeScript 5.1.6.

Take a look at Fresh 1.2, the latest release of our next-gen web framework.