Run ESLint rules against JavaScript or TypeScript code with configurable rule sets and auto-fix preview.
ESLint Playground evaluates a JavaScript or TypeScript snippet against the rule configuration you choose, then reports rule violations and shows an auto-fix preview when enabled rules provide fixes. It is useful for isolating one lint decision without setting up a project. The main surprise is that ESLint behavior is configuration-dependent: changing the language mode, rule options, or severity can change the result, and a clean result only means the selected rules found nothing.
Paste a source snippet, choose JavaScript or TypeScript as appropriate, and configure the ESLint rules to evaluate. Each enabled rule can be assigned a severity and, where supported, options. The result associates findings with source locations and rule identifiers when applicable, helping distinguish a parsing failure from a violation reported by a particular rule.
Auto-fix preview applies only fixes offered by enabled, fixable rules and displays the resulting source for inspection. A reported problem can remain after the preview if its rule has no automatic fix, if the fix would be unsafe, or if the configuration produces another finding. Treat the preview as proposed code, not proof that behavior is unchanged.
Not necessarily. A project can load shareable configurations, plugins, file-specific overrides, declared globals, parser settings, ignored paths, and a different ESLint version. The playground result is comparable only when the relevant language and rule configuration match. Use it to isolate a rule, then confirm the same snippet with the project's actual lint command.
ESLint rules are not required to provide fixes, and some deliberately report situations that need human judgment. Fixes also depend on the rule's options and the exact source. The preview can therefore change some findings while leaving others. No, the presence of a diagnostic does not imply that the playground can rewrite it safely.
The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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