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ESLint

by OpenJS Foundation · CLI tool

Pluggable static analysis tool for JavaScript and TypeScript that finds problems in code through configurable rules and can fix many automatically

MIT licenseOpen sourceFreeLocalCloudSelf-hostable
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Link verified Nov 2, 2026

Overview

ESLint is a linter for JavaScript and TypeScript maintained under the OpenJS Foundation and released under the MIT license. It parses source files into an abstract syntax tree and runs a configurable set of rules against it, reporting errors or warnings and applying automatic fixes where a rule supports them. Rules cover correctness issues, questionable patterns and style, and are grouped into shareable configurations published as npm packages.

The plugin system is the reason for its reach: typescript-eslint adds type-aware rules, and plugins exist for React, Vue, Node.js, imports, accessibility and most frameworks. Since version 9 the default configuration format is the flat eslint.config.js file, which replaced the older .eslintrc hierarchy; the migration is a common upgrade task in existing projects. ESLint runs from the command line, in CI and inside editors through the official extension. Its limitations are speed on large codebases, especially with type-aware rules, and configuration complexity when many plugins interact; this is the space where Biome positions itself as a faster alternative, and ESLint has in turn added language plugins for JSON, Markdown and CSS to broaden its scope.

Capabilities

  • Configurable rules with automatic fixes
  • Plugin ecosystem including type-aware TypeScript rules
  • Shareable configurations distributed via npm
  • Flat configuration file (eslint.config.js)
  • Editor integration and CI reporting formats
  • Language plugins for JSON, Markdown and CSS

Typical workflows

  1. Enforce a shared rule set across a monorepo
  2. Fail CI on lint errors and auto-fix locally on save
  3. Add type-aware rules to a TypeScript project

Strengths

  • Largest rule and plugin ecosystem for JavaScript
  • Highly configurable
  • MIT license, foundation governance

Limitations

  • Slower than Rust-based linters on large codebases
  • Configuration can become complex with many plugins
  • Flat config migration required for older projects

Prerequisites

  • Node.js and npm, pnpm or Bun

Who it is for

  • JavaScript and TypeScript developers
  • Teams enforcing coding standards

Alternatives & comparison

Biome combines linting and formatting in one Rust binary and is considerably faster, but supports fewer rules and plugins than the ESLint ecosystem. Prettier is a formatter rather than a linter; the two are commonly used together with ESLint handling correctness rules and Prettier handling layout.

  • Biome

    Rust-based formatter and linter for JavaScript, TypeScript, JSX, JSON, CSS and GraphQL that replaces Prettier and ESLint with one binary

    Open sourceOpen source
  • Prettier

    Opinionated code formatter for JavaScript, TypeScript, CSS, HTML, Markdown, YAML and more that reprints code from its syntax tree with few options

    Open sourceOpen source
Compare ESLint with its alternatives →

Sources & verification

Primary sources consulted for this record. Claims are tied to the fields each source supports; the automated link checker re-verifies every URL on a schedule.

Confidence
High
Reviewed
Nov 1, 2026
Links
Verified · Nov 2, 2026

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