# What changed in web-streams-polyfill

> 3 changes in web-streams-polyfill 4 from its official release notes, upgrade guides and advisories. Each one cited. Sources checked 2026-10-18. HTML: https://unstale.sh/npm/web-streams-polyfill/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## web-streams-polyfill 4

### Performance

- When a chunk is available in the stream’s internal queue, reads now return a resolved promise using Promise.resolve(), which is slightly faster. (4.3.0) — [release notes](https://github.com/MattiasBuelens/web-streams-polyfill/releases/tag/v4.3.0)
- When a chunk is available in the stream’s internal queue, reads now return a resolved promise using Promise.resolve(), which is slightly faster. (4.3.0) — [release notes](https://github.com/MattiasBuelens/web-streams-polyfill/releases/tag/v4.3.0)

### Behavior and default changes

- When chunks are available in the internal queue, pipeTo() reads them in a single batch and writes them to the destination while respecting backpressure. (4.3.0) — [release notes](https://github.com/MattiasBuelens/web-streams-polyfill/releases/tag/v4.3.0)