We're looking for a user researcher to understand the needs of developers and designers. Is this you or someone you know? Check out the post: https://mzl.la/2IGzdXS

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The ReadableStream interface of the Streams API represents a readable stream of byte data. The Fetch API offers a concrete instance of a ReadableStream through the body property of a Response object.


Creates and returns a readable stream object from the given handlers.


ReadableStream.locked Read only
The locked getter returns whether or not the readable stream is locked to a reader.


Cancels the stream, signaling a loss of interest in the stream by a consumer. The supplied reason argument will be given to the underlying source, which may or may not use it.
Creates a reader and locks the stream to it. While the stream is locked, no other reader can be acquired until this one is released.
Provides a chainable way of piping the current stream through a transform stream or any other writable/readable pair.
Pipes the current ReadableStream to a given WritableStream and returns a promise that fulfills when the piping process completes successfully, or rejects if any errors were encountered.
The tee method tees this readable stream, returning a two-element array containing the two resulting branches as new ReadableStream instances.


In the following example, an artifical Response is created to stream HTML fragments fetched from another resource to the browser.

It demonstrates the usage of a ReadableStream in combination with a Uint8Array.

fetch("https://www.example.org/").then((response) => {
  const reader = response.body.getReader();
  const stream = new ReadableStream({
    start(controller) {
      // The following function handles each data chunk
      function push() {
        // "done" is a Boolean and value a "Uint8Array"
        reader.read().then(({ done, value }) => {
          // Is there no more data to read?
          if (done) {
            // Tell the browser that we have finished sending data

          // Get the data and send it to the browser via the controller

  return new Response(stream, { headers: { "Content-Type": "text/html" } });


Specification Status Comment
The definition of 'ReadableStream' in that specification.
Living Standard Initial definition

Browser Compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support4316571 No30 ?
ReadableStream() constructor4316571 No30 ?
locked4316571 No30 ?
cancel4316571 No30 ?
getReader4316571 No30 ?
pipeThrough59 ?571 No46 ?
pipeTo59 ?571 No46 ?
tee4316571 No30 ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support43431657130 ?4.0
ReadableStream() constructor43431657130 ?4.0
locked43431657130 ?4.0
cancel43431657130 ?4.0
getReader43431657130 ?4.0
pipeThrough5959 ?57146 ?7.0
pipeTo5959 ?57146 ?7.0
tee43431657130 ?4.0

1. From version 57: this feature is behind the dom.streams.enabled preference (needs to be set to true) and the javascript.options.streams preference (needs to be set to true). To change preferences in Firefox, visit about:config.

Document Tags and Contributors

Last updated by: anthumchris,