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.eslintrc

What is a .eslintrc file?

Legacy ESLint config — code style and quality rules for JavaScript/TypeScript. Replaced by `eslint.config.js` (flat config) in ESLint 9.

Safe format
Type Code
By Nicholas C. Zakas (ESLint)
MIME application/json

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What is it

ESLint is the dominant linter for JavaScript and TypeScript. .eslintrc was its original config file: extends a base preset (airbnb, standard, recommended), declares custom rules, configures plugins (`@typescript-eslint`, `eslint-plugin-react`), and sets parser options (target ES version, JSX support).

Format variants existed for taste — .eslintrc, .eslintrc.json, .eslintrc.js, .eslintrc.yml. ESLint reads any of them. The bare .eslintrc (no extension) holds JSON-formatted content and follows the dotfile-only naming convention popular in Node-land circa 2015. Newer projects tend to use .eslintrc.json (explicit format) or .eslintrc.js (when you need JavaScript expressions in the config).

ESLint 9 (April 2024) deprecated this format in favour of `eslint.config.js` — the new "flat config" — which simplifies inheritance, makes parsing rules clearer, and ditches some legacy quirks. Legacy .eslintrc still works in ESLint 9 with the `ESLINT_USE_FLAT_CONFIG=false` env var, but ESLint 10 will likely drop it entirely. Migration guide at eslint.org/docs/latest/use/configure/migration-guide.

Technical details
Full Name
.eslintrc
MIME Type
application/json
Developer
Nicholas C. Zakas (ESLint)
Magic Bytes
N/A
Safety
.eslintrc is a known, safe format.
What opens it
Any text editor
FREE All
VS Code
FREE All

* ESLint extension provides validation

FAQ
Should I migrate to flat config (eslint.config.js)?
Yes, eventually. ESLint 9 still supports the legacy .eslintrc format but ESLint 10 will likely drop it. New projects should start with eslint.config.js. Existing projects can migrate when convenient — there's a `@eslint/migrate-config` codemod that handles the bulk of the work.
What's the difference between .eslintrc and .eslintrc.json?
Functionally identical — both hold JSON content, both are read by ESLint with equal priority. The .eslintrc form is older convention; .eslintrc.json is more explicit and gets you JSON syntax highlighting in editors that don't recognise the bare form.
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