# What changed in addons-linter

> 14 changes in addons-linter 9 to 10 from its official release notes, upgrade guides and advisories: 4 breaking. Each one cited. Sources checked 2026-10-20. HTML: https://unstale.sh/npm/addons-linter/

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

## addons-linter 10

### Breaking changes

- The description field is limited to 250 characters. (10.14.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.14.0)
- Additional validation applies to static themes CSS gradients properties, affecting which themes pass linting. (10.8.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.8.0)
- Node 22 is now used by default. (10.0.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.0.0)
- The obsolete openDialog rules have been removed. (10.0.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.0.0)

### Behavior and default changes

- Imports API JSONSchema data from Gecko 154.0b4, which can affect validation of WebExtensions APIs. (10.10.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.10.0)

### Tooling

- Imported Firefox 158 schema data, allowing addons-linter to recognize its schema. (10.14.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.14.0)
- Imported schema data for Firefox 155, 156, and 157, adding support for these Firefox versions in addons-linter. (10.12.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.12.0)
- Schema data for Firefox 153.0b2 is imported, updating the browser data available to addons-linter. (10.8.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.8.0)
- Adds Firefox 149 schema data, allowing addons-linter to use that data when linting. (10.1.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.1.0)

### Fixes and other changes

- Usage of userScripts.onBeforeScript in MV2 no longer triggers a warning. (10.14.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.14.0)
- Fixed support for using update_url with enterprise add-ons. (10.11.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.11.0)
- Replacement values in l10n strings are no longer re-scanned. (10.9.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.9.0)
- Allows a placeholder to be replaced more than once in an l10n string. (10.8.1) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/10.8.1)

## addons-linter 9

### Behavior and default changes

- JavaScript is parsed using ECMA_VERSION 16. (9.9.0) — [release notes](https://github.com/mozilla/addons-linter/releases/tag/9.9.0)