# Migrate from ESLint to bun lint `bun lint` reads your `eslint.config.js` and prints the same report as ESLint 10. In most projects you only change the command. ```json package.json icon="file-json" { "scripts": { "lint": "eslint --max-warnings 0", // [!code --] "lint": "bun lint --max-warnings 0" // [!code ++] } } ``` Flags and arguments stay the same: `eslint --fix src` becomes `bun lint --fix src`. Change CI, lint-staged, and Git hooks too. Edit the script first. If `package.json` has a `lint` script, `bun lint` runs that script, so you'd still get ESLint. --- Run it. You get the same rules, messages, and exit code as with `eslint`. ```sh terminal icon="terminal" bun run lint ``` ```txt $ bun lint --max-warnings 0 /app/src/index.ts 1:1 warning Open an issue instead of leaving a TODO local/no-todo 3:7 error 'fallback' is never reassigned. Use 'const' instead prefer-const 4:27 error Invalid typeof comparison value valid-typeof ✖ 3 problems (2 errors, 1 warning) 1 error and 0 warnings potentially fixable with the `--fix` option. Linted 3 files [108.90ms] error: script "lint" exited with code 1 ``` --- Run `--doctor` to see what Bun does with your config. It doesn't lint or write anything. ```sh terminal icon="terminal" bun lint --doctor ``` ```txt Using eslint.config.js (ESLint flat config) 3 files to lint 25 rules run natively 1 rule runs in JavaScript lint/plugin.js 1 Still needed: eslint (typescript-eslint needs it) typescript-eslint (eslint.config.js loads it) ``` - **Natively**: the rule is built into Bun. That covers ESLint's core rules, typescript-eslint, `react`, `react-hooks`, `import`, 15 rules of `n`, and `prettier/prettier`. - **In JavaScript**: Bun loads the plugin and runs it like ESLint does. It works, but it's slower. See [ESLint plugins](/lint/plugins). The last lines tell you which packages you still need. Bun runs your `eslint.config.js`, so everything that file imports has to stay. Here that's `typescript-eslint`, which needs `eslint`. Packages you no longer need are listed under `You can remove`. --- You can drop lint-staged. `--staged` lints only the staged files, and with `--fix` it stages the fixed files again. ```sh .husky/pre-commit icon="terminal" npx lint-staged # [!code --] bun lint --staged --fix # [!code ++] ``` --- Type-aware rules need no changes. If your config asks for types, they run. ```js eslint.config.js icon="/icons/javascript.svg" import tseslint from "typescript-eslint"; export default tseslint.config(...tseslint.configs.recommendedTypeChecked, { languageOptions: { parserOptions: { projectService: true } }, }); ``` The types come from Bun's built-in type checker ([`bun check`](/runtime/check)), not from the `typescript` package. It behaves like TypeScript 7. --- Still on ESLint 8? `.eslintrc.*`, `eslintConfig` in `package.json`, and `.eslintignore` work when there is no `eslint.config.js`. So do ESLint 8's flags. ```sh terminal icon="terminal" eslint --ext .js,.ts,.tsx src # [!code --] bun lint --ext .js,.ts,.tsx src # [!code ++] ``` --- If your config asks for something Bun can't do, Bun lints everything else, tells you what it skipped, and exits with code `2`. ```txt error: 1 rule did not run because rules that run in JavaScript cannot use type information: local/typed Everything else was linted. Use --allow-unsupported to make this a warning. ``` There are two such cases: a JavaScript rule that needs types, and files in [other languages](/lint/plugins#other-languages) when the `eslint` package isn't installed. Pass `--allow-unsupported` to turn the error into a warning. --- If the project also has an oxlint config, Bun uses that one and tells you. ```txt note: Using .oxlintrc.json. eslint.config.js is ignored. Use --config to pick it. ``` Pick the ESLint config with `--config`. ```json package.json icon="file-json" { "scripts": { "lint": "oxlint && eslint", // [!code --] "lint": "bun lint && bun lint --config eslint.config.js" // [!code ++] } } ``` --- ## Differences from ESLint If `bun lint` and ESLint 10 disagree about a rule, that's a bug. [Open an issue](https://github.com/oven-sh/bun/issues). These differences are intentional: - **Built-in rules have a fixed version**, whatever you have installed: ESLint 10.12, typescript-eslint 8.71, eslint-plugin-react 7.37, react-hooks 7.1, import 2.32, n 18.4. [`--no-native-plugin-rules`](/lint/plugins#run-the-installed-package-instead) runs your installed plugins instead. - **Deprecated formatting rules don't run**: `semi`, `quotes`, `indent`, and so on. Use [`bun fmt`](/format) or `@stylistic/eslint-plugin`. - **No custom formatters.** `-f` only takes built-in formats such as `stylish`, `json`, `unix`, `junit`, and `sarif`. - **No `--inspect-config` or `--mcp`.** - **`--cache` does nothing.** Every run lints every file. - **No config file is not an error.** Bun uses [its defaults](/lint#default-rules). - **Syntax errors can be worded differently.** Bun's parser replaces `espree`, `@typescript-eslint/parser`, and `@babel/eslint-parser`. - **A type-aware rule without type information is skipped**, with a warning. typescript-eslint throws. - **A file that no `tsconfig.json` includes is still linted**, with the nearest `tsconfig.json`. ESLint stops. - **`--fix` never writes a file that no longer parses.** Bun drops those fixes and warns. - **`console.log` in your config file is hidden** unless the config fails to load. - **One extra line on stderr** with the number of files and the time. - **In GitHub Actions, `::error` and `::warning` lines follow the `stylish` report** on stdout, so problems show up in the pull request diff. If a problem matcher such as the one from `actions/setup-node` already does that, you get each annotation twice. `-f json` and the other machine-readable formats don't have these lines. --- See also: - [`bun lint`](/lint) - [ESLint plugins](/lint/plugins) - [Migrate from Prettier to bun fmt](/guides/format/migrate-from-prettier)