# What changed in flatbush

> 10 changes in flatbush 4 from its official release notes, upgrade guides and advisories: 3 breaking. Each one cited. Sources checked 2026-10-23. HTML: https://unstale.sh/npm/flatbush/

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

## flatbush 4

### Breaking changes

- Bundle transpiling is dropped; users can still transpile on their end. (4.0.0) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.0.0)
- The CommonJS entry point is dropped in favor of an ESM-only Node entry point. (4.0.0) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.0.0)
- Support for IE11 is dropped; users can still handle this on their end. (4.0.0) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.0.0)

### Performance

- neighbors search is 12–18% faster for small k and 33% faster for k = 1. (4.6.2) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.6.2)
- Indexing is 2-3% faster. (4.6.1) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.6.1)
- Search is up to 9% faster on large queries. (4.6.1) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.6.1)
- Indexing is 9% faster. (4.6.0) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.6.0)
- kNN is 5% faster. (4.6.0) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.6.0)
- Large search queries are much faster, about 20–50% when queries contain many items. (4.6.0) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.6.0)

### Fixes and other changes

- Fixes an edge case that could lead to stack overflow by switching to non-recursive quicksort. (4.5.1) — [release notes](https://github.com/mourner/flatbush/releases/tag/v4.5.1)