GeezerVison

The benchmark is a simple getting data [example](https://github.com/nodejs/undici/blob/main/benchmarks/benchmark.js) using a

50 TCP connections with a pipelining depth of 10 running on Node 22.11.0.

The benchmark is a simple getting data [example](https://github.com/nodejs/undici/blob/main/benchmarks/benchmark.js) using

50 TCP connections with a pipelining depth of 10 running on Node 24.14.1.

Using [benchmark-https.js](https://github.com/nodejs/undici/blob/main/benchmarks/benchmark-https.js) against an h1-over-TLS server (50 connections, pipelining depth 10, Node 24.14.1).

Using [benchmark-http2.js](https://github.com/nodejs/undici/blob/main/benchmarks/benchmark-http2.js) against an h2 server (50 connections, pipelining depth 10, Node 24.14.1).

Example usage:

Undici aligns with the Node.js LTS schedule. The following table shows the supported versions:

| Undici Version | Bundled in Node.js | Node.js Versions Supported | End of Life |

|----------------|-------------------|----------------------------|-------------|

| 5.x | 18.x | ≥14.0 (tested: 14, 16, 18) | 2024-04-30 |

| 6.x | 20.x, 22.x | ≥18.17 (tested: 18, 20, 21, 22) | 2026-04-30 |

| 7.x | 24.x | ≥20.18.1 (tested: 20, 22, 24) | 2027-04-30 |

|----------------|--------------------|----------------------------|-------------|

| 5.x | 18.x | ≥14.0 (tested: 14, 16, 18) | 2024-04-30 |

| 6.x | 20.x, 22.x | ≥18.17 (tested: 18, 20, 21, 22) | 2027-04-30 |

| 7.x | 24.x | ≥20.18.1 (tested: 20, 22, 24) | 2028-04-30 |

| 8.x | 26.x | ≥22.19.0 (tested: 22, 24, 26) | 2029-04-30 |

**Undici trusts**:

* The application code that uses its APIs, including all configuration,

options, and callbacks provided by the application.

options, callbacks, and decisions about which body-consuming APIs to call.

* The operating system and its network stack.

* The Node.js runtime undici is running on.

* Dependencies installed by the application.

resources, that is not considered a vulnerability. Applications are

responsible for setting appropriate limits on response sizes.

* `body.formData()` buffers and parses the entire response body. Multipart

parsing has inherent security risks, especially when the body is supplied by

an untrusted or user-controlled server. Applications must only call

`body.formData()` on responses from trusted servers. For untrusted responses,

applications should use a dedicated streaming multipart parser and enforce

application-specific limits. Resource exhaustion or parser exposure caused by

calling `body.formData()` on untrusted responses is considered an application

responsibility, not a vulnerability in undici.

* Issues arising from incorrect or insecure use of undici APIs (such as

* **factory** `(origin: URL, opts: Object) => Dispatcher` - Default: `(origin, opts) => new Pool(origin, opts)`

* **maxOrigins** `number` (optional) - Default: `Infinity` - Limits the total number of origins that can receive requests at a time, throwing an `MaxOriginsReachedError` error when attempting to dispatch when the max is reached. If `Infinity`, no limit is enforced.

* **maxResponseSize** `number | null` (optional) - Default: `-1` - The maximum length of response body in bytes. Set to `-1` to disable.

* **webSocket** `WebSocketOptions` (optional) - WebSocket-specific configuration options.

* **maxPayloadSize** `number` (optional) - Default: `134217728` (128 MB) - Maximum allowed payload size in bytes for WebSocket messages. Applied to uncompressed messages, compressed frame payloads, and decompressed (permessage-deflate) messages. Set to 0 to disable the limit.

* **pipelining** `number | null` (optional) - Default: `1` - The amount of concurrent requests to be sent over the single TCP/TLS connection according to [RFC7230](https://tools.ietf.org/html/rfc7230#section-6.3.2). Carefully consider your workload and environment before enabling concurrent requests as pipelining may reduce performance if used incorrectly. Pipelining is sensitive to network stack settings as well as head of line blocking caused by e.g. long running requests. Set to `0` to disable keep-alive connections.

* **connect** `ConnectOptions | Function | null` (optional) - Default: `null`.

* **pipelining** `number | null` (optional) - Default: `1` - The amount of concurrent requests to be sent over the single TCP/TLS connection according to [RFC7230](https://tools.ietf.org/html/rfc7230#section-6.3.2). Carefully consider your workload and environment before enabling concurrent requests as pipelining may reduce performance if used incorrectly. Pipelining is sensitive to network stack settings as well as head of line blocking caused by e.g. long running requests. Set to `0` to disable keep-alive connections. This option has no effect once HTTP/2 is negotiated — see `maxConcurrentStreams` for the h2 dispatch ceiling.

* **connect** `ConnectOptions | Function | null` (optional) - Default: `null` - Configures how undici establishes TCP/TLS connections. Accepts two forms:

* **Object (`ConnectOptions`)**: Options passed directly to the internal [`buildConnector()`](/docs/docs/api/Connector.md). This is the simplest way to customize TLS or socket behavior (e.g., setting `rejectUnauthorized`, `ca`, `socketPath`). See [`ConnectOptions`](#parameter-connectoptions) for available fields.

* **Function**: A custom connector with the signature `(options, callback)`, where `options` contains `{ hostname, host, protocol, port, servername, localAddress, httpSocket }` and `callback` follows `(error, socket)`. Useful when you need full control over socket creation, such as adding custom validation or proxy logic. When a function is provided, undici wraps it to automatically inject `socketPath` and `allowH2` into the `options` argument if those values are set on the client.

* **strictContentLength** `Boolean` (optional) - Default: `true` - Whether to treat request content length mismatches as errors. If true, an error is thrown when the request content-length header doesn't match the length of the request body. **Security Warning:** Disabling this option can expose your application to HTTP Request Smuggling attacks, where mismatched content-length headers cause servers and proxies to interpret request boundaries differently. This can lead to cache poisoning, credential hijacking, and bypassing security controls. Only disable this in controlled environments where you fully trust the request source.

* **autoSelectFamily**: `boolean` (optional) - Default: depends on local Node version, on Node 18.13.0 and above is `false`. Enables a family autodetection algorithm that loosely implements section 5 of [RFC 8305](https://tools.ietf.org/html/rfc8305#section-5). See [here](https://nodejs.org/api/net.html#socketconnectoptions-connectlistener) for more details. This option is ignored if not supported by the current Node version.

* **autoSelectFamilyAttemptTimeout**: `number` - Default: depends on local Node version, on Node 18.13.0 and above is `250`. The amount of time in milliseconds to wait for a connection attempt to finish before trying the next address when using the `autoSelectFamily` option. See [here](https://nodejs.org/api/net.html#socketconnectoptions-connectlistener) for more details.

* **allowH2**: `boolean` - Default: `true`. Enables support for H2 if the server has assigned bigger priority to it through ALPN negotiation.

* **useH2c**: `boolean` - Default: `false`. Enforces h2c for non-https connections.

* **maxConcurrentStreams**: `number` - Default: `100`. Dictates the maximum number of concurrent streams for a single H2 session. It can be overridden by a SETTINGS remote frame.

* **maxConcurrentStreams**: `number` - Default: `100`. The maximum number of concurrent HTTP/2 streams per session. When `allowH2` negotiates h2, this — not `pipelining` (which is HTTP/1.1 only, per [RFC7230](https://tools.ietf.org/html/rfc7230#section-6.3.2)) — is the ceiling the Client uses to dispatch in-flight requests on a shared session. The same value is advertised to the server as `peerMaxConcurrentStreams`, capping how many streams the server may push back. The initial value is replaced by the server's `SETTINGS_MAX_CONCURRENT_STREAMS` whenever the server sends one, so a user-supplied value acts as a pre-`SETTINGS` default rather than a hard cap.

* **initialWindowSize**: `number` (optional) - Default: `262144` (256KB). Sets the HTTP/2 stream-level flow-control window size (SETTINGS_INITIAL_WINDOW_SIZE). Must be a positive integer greater than 0. This default is higher than Node.js core's default (65535 bytes) to improve throughput, Node's choice is very conservative for current high-bandwith networks. See [RFC 7540 Section 6.9.2](https://datatracker.ietf.org/doc/html/rfc7540#section-6.9.2) for more details.

* **connectionWindowSize**: `number` (optional) - Default `524288` (512KB). Sets the HTTP/2 connection-level flow-control window size using `ClientHttp2Session.setLocalWindowSize()`. Must be a positive integer greater than 0. This provides better flow control for the entire connection across multiple streams. See [Node.js HTTP/2 documentation](https://nodejs.org/api/http2.html#clienthttp2sessionsetlocalwindowsize) for more details.

* **pingInterval**: `number` - Default: `60e3`. The time interval in milliseconds between PING frames sent to the server. Set to `0` to disable PING frames. This is only applicable for HTTP/2 connections. This will emit a `ping` event on the client with the duration of the ping in milliseconds.

const client = new Client('http://localhost:3000')

This will allow you to perform some additional check on the socket that will be used for the next request.

Pass a `ConnectOptions` object to customize the TLS connection. The options are forwarded to the internal `buildConnector()`.

import { Client } from 'undici'

import fs from 'node:fs'

const client = new Client('https://localhost:3000', {

connect: {

rejectUnauthorized: false,

ca: fs.readFileSync('./ca-cert.pem')

}

})

Use the `socketPath` option to connect through an IPC endpoint instead of a TCP connection.

import { Client } from 'undici'

const client = new Client('http://localhost:3000', {

connect: {

socketPath: '/var/run/docker.sock'

}

})

Pass a function for full control over socket creation. This allows you to perform additional checks on the socket, use a proxy, or implement custom connection logic.

})

For more details on building custom connectors, see [Connector](/docs/docs/api/Connector.md).