# What changed in postcss-preset-env

> 3 changes in postcss-preset-env 11 from its official release notes, upgrade guides and advisories: 1 new APIs and options. Each one cited. Sources checked 2026-10-19. HTML: https://unstale.sh/npm/postcss-preset-env/

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

## postcss-preset-env 11

### New APIs and options

- Added @csstools/postcss-custom-functions to postcss-preset-env. (11.6.0) — [release notes](https://github.com/csstools/postcss-plugins/blob/d70aa9feebea5a3534fbcc1deb202294437c7ce6/plugin-packs/postcss-preset-env/CHANGELOG.md#1160)

### Performance

- Many plugins now have bounds to prevent CPU starvation or out-of-memory conditions. (11.5.5) — [release notes](https://github.com/csstools/postcss-plugins/blob/d70aa9feebea5a3534fbcc1deb202294437c7ce6/plugin-packs/postcss-preset-env/CHANGELOG.md#1155)

### Behavior and default changes

- Implements more of the current spec, changing how mixins are processed. (11.5.5) — [release notes](https://github.com/csstools/postcss-plugins/blob/d70aa9feebea5a3534fbcc1deb202294437c7ce6/plugin-packs/postcss-preset-env/CHANGELOG.md#1155)