ReadableByteStreamController: close() method

Baseline 2026

Newly available

Since March 2026, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

Note: This feature is available in Web Workers.

The close() method of the ReadableByteStreamController interface closes the associated stream.

This might be called by the underlying source when its data source has been exhausted/completed.

Note: Readers will still be able to read any previously-enqueued chunks from the stream, but once those are read, the stream will become closed. However if there is an outstanding and partially written byobRequest when close() is called, the stream will be errored.

Syntax

close()

Parameters

None.

Return value

None (undefined).

Exceptions

TypeError

Thrown if the source object is not a ReadableByteStreamController, it is already closed, or the stream is not readable for some other reason.

Examples

The example in Using readable byte streams > Creating a readable socket push byte stream how we might close the stream when there is no more data.

The relevant code is reproduced below. This relies on the hypothetical readInto() method returning 0 bytes only when there is no more data.

js
bytesRead = socket.readInto(v.buffer, v.byteOffset, v.byteLength);
if (bytesRead === 0) {
  controller.close();
}

After calling close, the stream will be closed, and any consumers signalled. For example if using a ReadableStreamBYOBReader any read() requests would resolve with done: true and the promise from ReadableStreamBYOBReader.closed would also be resolved.