ESLint v9.9.0 released

Highlights

Here are some of the key changes in this release.

Experimental TypeScript configuration files

Arya Emami landed experimental support for TypeScript configuration files. Specifically, you can now use eslint.config.ts, eslint.config.mts, and eslint.config.cts files as your configuration files. Because this feature is experimental, you’ll need to use the unstable_ts_config feature flag:

npx eslint --flag unstable_ts_config
1

For Node.js, you’ll need to manually install jiti, which provides the TypeScript-to-JavaScript functionality; for Deno and Bun, no additional dependency is necessary. (When TypeScript type stripping lands as stable in Node.js, you also won’t need an additional dependency in Node.js)

For more information on this feature, see TypeScript Configuration Files. For more information on using feature flags, see Feature Flags.

Other notable changes

The require-await rule now suggests to remove possibly unnecessary usages of the async keyword.

Features

• 41d0206 feat: Add support for TS config files (#18134) (Arya Emami)
• 3a4eaf9 feat: add suggestion to require-await to remove async keyword (#18716) (Dave)

Documentation

• 9fe068c docs: how to author plugins with configs that extend other configs (#18753) (Alec Gibson)
• 48117b2 docs: add version support page in the side navbar (#18738) (Amaresh S M)
• fec2951 docs: add version support page to the dropdown (#18730) (Amaresh S M)
• 38a0661 docs: Fix typo (#18735) (Zaina Al Habash)
• 3c32a9e docs: Update yarn command for creating ESLint config (#18739) (Temitope Ogunleye)
• f9ac978 docs: Update README (GitHub Actions Bot)

Chores

• 461b2c3 chore: upgrade to @eslint/js@9.9.0 (#18765) (Francesco Trotta)
• 59dba1b chore: package.json update for @eslint/js release (Jenkins)
• fea8563 chore: update dependency @eslint/core to ^0.3.0 (#18724) (renovate[bot])
• aac191e chore: update dependency @eslint/json to ^0.3.0 (#18760) (renovate[bot])
• b97fa05 chore: update wdio dependencies for more stable tests (#18759) (Christian Bromann)