undici

An HTTP/1.1 client, written from scratch for Node.js.

Undici means eleven in Italian. 1.1 -> 11 -> Eleven -> Undici. It is also a Stranger Things reference.

How to get involved

Have a question about using Undici? Open a Q&A Discussion or join our official OpenJS Slack channel.

Looking to contribute? Start by reading the contributing guide

Install

npm i undici

Benchmarks

The benchmark is a simple getting data example using 50 TCP connections with a pipelining depth of 10 running on Node 24.14.1.

HTTP/1.1

┌────────────────────────┬─────────┬────────────────────┬────────────┬─────────────────────────┐
│  Tests                 │ Samples │ Result             │ Tolerance  │ Difference with slowest │
├────────────────────────┼─────────┼────────────────────┼────────────┼─────────────────────────┤
│  'node-fetch'          │ 50      │ '4711.86 req/sec'  │ '± 2.92 %' │ '-'                     │
│  'undici - fetch'      │ 75      │ '5438.50 req/sec'  │ '± 2.97 %' │ '+ 15.42 %'             │
│  'axios'               │ 45      │ '5448.08 req/sec'  │ '± 2.98 %' │ '+ 15.62 %'             │
│  'request'             │ 65      │ '5809.63 req/sec'  │ '± 2.90 %' │ '+ 23.30 %'             │
│  'http - no keepalive' │ 35      │ '5910.77 req/sec'  │ '± 2.87 %' │ '+ 25.44 %'             │
│  'got'                 │ 50      │ '6047.80 req/sec'  │ '± 2.91 %' │ '+ 28.35 %'             │
│  'superagent'          │ 60      │ '7534.53 req/sec'  │ '± 2.97 %' │ '+ 59.91 %'             │
│  'http - keepalive'    │ 75      │ '9343.41 req/sec'  │ '± 2.90 %' │ '+ 98.30 %'             │
│  'undici - pipeline'   │ 65      │ '13470.70 req/sec' │ '± 2.93 %' │ '+ 185.89 %'            │
│  'undici - request'    │ 80      │ '16850.87 req/sec' │ '± 2.93 %' │ '+ 257.63 %'            │
│  'undici - stream'     │ 101     │ '18488.56 req/sec' │ '± 3.81 %' │ '+ 292.38 %'            │
│  'undici - dispatch'   │ 101     │ '20786.44 req/sec' │ '± 3.08 %' │ '+ 341.15 %'            │
└────────────────────────┴─────────┴────────────────────┴────────────┴─────────────────────────┘

HTTP/1.1 over HTTPS

Using benchmark-https.js against an h1-over-TLS server (50 connections, pipelining depth 10, Node 24.14.1).

┌────────────────────────┬─────────┬───────────────────┬────────────┬─────────────────────────┐
│  Tests                 │ Samples │ Result            │ Tolerance  │ Difference with slowest │
├────────────────────────┼─────────┼───────────────────┼────────────┼─────────────────────────┤
│  'https - no keepalive'│ 10      │ '1358.40 req/sec' │ '± 1.99 %' │ '-'                     │
│  'undici - fetch'      │ 30      │ '3721.76 req/sec' │ '± 2.97 %' │ '+ 173.98 %'            │
│  'https - keepalive'   │ 35      │ '5633.91 req/sec' │ '± 2.84 %' │ '+ 314.75 %'            │
│  'undici - pipeline'   │ 15      │ '6254.05 req/sec' │ '± 2.80 %' │ '+ 360.40 %'            │
│  'undici - request'    │ 25      │ '6669.80 req/sec' │ '± 2.73 %' │ '+ 391.01 %'            │
│  'undici - stream'     │ 25      │ '7019.04 req/sec' │ '± 2.77 %' │ '+ 416.71 %'            │
│  'undici - dispatch'   │ 20      │ '7361.85 req/sec' │ '± 2.90 %' │ '+ 441.95 %'            │
└────────────────────────┴─────────┴───────────────────┴────────────┴─────────────────────────┘

HTTP/2

Using benchmark-http2.js against an h2 server (50 connections, pipelining depth 10, Node 24.14.1).

┌────────────────────────┬─────────┬───────────────────┬────────────┬─────────────────────────┐
│  Tests                 │ Samples │ Result            │ Tolerance  │ Difference with slowest │
├────────────────────────┼─────────┼───────────────────┼────────────┼─────────────────────────┤
│  'undici - fetch'      │ 45      │ '3499.03 req/sec' │ '± 2.93 %' │ '-'                     │
│  'native - http2'      │ 25      │ '4904.58 req/sec' │ '± 2.81 %' │ '+ 40.17 %'             │
│  'undici - pipeline'   │ 60      │ '5836.82 req/sec' │ '± 2.99 %' │ '+ 66.81 %'             │
│  'undici - request'    │ 65      │ '6831.25 req/sec' │ '± 2.83 %' │ '+ 95.23 %'             │
│  'undici - stream'     │ 55      │ '6874.30 req/sec' │ '± 2.91 %' │ '+ 96.46 %'             │
│  'undici - dispatch'   │ 55      │ '7791.23 req/sec' │ '± 2.96 %' │ '+ 122.67 %'            │
└────────────────────────┴─────────┴───────────────────┴────────────┴─────────────────────────┘

Undici vs. Fetch

Overview

Node.js includes a built-in fetch() implementation powered by undici starting from Node.js v18. However, there are important differences between using the built-in fetch and installing undici as a separate module.

WebAssembly requirement

Undici's HTTP/1 parser requires WebAssembly. There is no alternative parser when WebAssembly is unavailable, for example in Node.js configurations where --jitless disables it. The existence of fetch does not imply that it can make HTTP/1 requests in that environment.

This is the beginning of the README. Read the rest at the original. Read the full README ↗