# What changed in postcss-custom-properties

> 7 changes in postcss-custom-properties 15 from its official release notes, upgrade guides and advisories: 3 breaking. Each one cited. Sources checked 2026-10-24. HTML: https://unstale.sh/npm/postcss-custom-properties/

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

## postcss-custom-properties 15

### Breaking changes

- A single expansion budget is shared across all declarations. (15.0.4) — [release notes](https://github.com/csstools/postcss-plugins/blob/51138b0c4a17413a0f4751aa89d32b505ac4a777/plugins/postcss-custom-properties/CHANGELOG.md#1504)
- Throws when a custom property expansion exceeds the maximum size. (15.0.2) — [release notes](https://github.com/csstools/postcss-plugins/blob/51138b0c4a17413a0f4751aa89d32b505ac4a777/plugins/postcss-custom-properties/CHANGELOG.md#1502)
- Throws when @layer nesting exceeds a safe depth. (15.0.2) — [release notes](https://github.com/csstools/postcss-plugins/blob/51138b0c4a17413a0f4751aa89d32b505ac4a777/plugins/postcss-custom-properties/CHANGELOG.md#1502)

### Performance

- Avoids a quadratic sibling scan when checking for an existing fallback declaration. (15.0.4) — [release notes](https://github.com/csstools/postcss-plugins/blob/51138b0c4a17413a0f4751aa89d32b505ac4a777/plugins/postcss-custom-properties/CHANGELOG.md#1504)
- Sorting a long chain of custom properties is faster and avoids a stack overflow. (15.0.2) — [release notes](https://github.com/csstools/postcss-plugins/blob/51138b0c4a17413a0f4751aa89d32b505ac4a777/plugins/postcss-custom-properties/CHANGELOG.md#1502)

### Fixes and other changes

- Custom properties in @function bodies are ignored. (15.0.4) — [release notes](https://github.com/csstools/postcss-plugins/blob/51138b0c4a17413a0f4751aa89d32b505ac4a777/plugins/postcss-custom-properties/CHANGELOG.md#1504)
- Fix exponential growth of cascade layer names for deeply nested @layer rules. (15.0.2) — [release notes](https://github.com/csstools/postcss-plugins/blob/51138b0c4a17413a0f4751aa89d32b505ac4a777/plugins/postcss-custom-properties/CHANGELOG.md#1502)