k6 experimental streams WritableStream and WritableStreamDefaultWriter

Introduced 2026-08-10 · score 0.93

HOW TO USE IT

When implementing a writable stream in k6 v2.2.0, import `WritableStream` from `k6/experimental/streams`. Create it with a `write` handler, then call `getWriter()`, `write()`, and `close()` as shown.

import { WritableStream } from 'k6/experimental/streams';

export default async function () {
  const stream = new WritableStream({
    write(chunk) {
      console.log(`wrote ${chunk}`);
    },
  });

  const writer = stream.getWriter();
  await writer.write('hello');
  await writer.close();
}

WHY THIS HELPS

When implementing a writable stream in a k6 script, use the experimental streams module.

REQUIREMENTS AND LIMITATIONS

Version: v2.2.0
Availability: Experimental streams module.
write(chunk): The example’s underlying sink handler receives a chunk and logs it. The release note does not document whether the handler is required.
writer.write('hello') (required): Writes the `hello` chunk in the documented example.
writer.close() (required): Closes the writer in the documented example.
Prerequisite: Use k6 v2.2.0 or later for the release-note implementation described here; the module is experimental.
Prerequisite: Install k6 to write and execute k6 scripts.
Implements WritableStream and WritableStreamDefaultWriter following the WHATWG Streams specification.

FIRST-PARTY EVIDENCE

Check the installed version and the source before using it. Entry JSON

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Changes

k6 experimental streams WritableStream and WritableStreamDefaultWriter