Transferable streams permit you to run code like worker.postMessage(stream, [stream]) where stream is a ReadableStream, WritableStream or TransformStream and have it do what you'd expect. The explainer goes into more detail of why you'd want to do this, but briefly it provides a convenient way to do thread-offloading for streams-using code.

The pull-request for the standard is at https://github.com/whatwg/streams/issues/276 and the web platform tests are at https://github.com/web-platform-tests/wpt/pull/24546.

Any and all feedback is welcome!

Thanks,

Adam Rice, Chromium