ReadableStreamBYOBReader: closed property

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 closed read-only property of the ReadableStreamBYOBReader interface returns a Promise that fulfills when the stream closes, or rejects if the stream throws an error or the reader's lock is released.

This property enables you to write code that responds to an end to the streaming process.

Value

A Promise.

Examples

The code below shows the pattern for handling the closed/error state of a BYOBReader.

const reader = stream.getReader({ mode: "byob" });
reader.closed
  .then(() => {
    // Resolved - code to handle stream closing
  })
  .catch(() => {
    // Rejected - code to handle error
  });