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ESLint
JavaScript and TypeScript linter — 43 million weekly downloads, catches bugs before runtime, configurable rules.
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About ESLint
ESLint is the JavaScript and TypeScript static analysis tool that catches bugs, enforces code style, and prevents common mistakes before your code runs. 43 million weekly npm downloads make it the most widely used code quality tool in the JavaScript ecosystem.
What ESLint catches that TypeScript does not: no-unused-vars (variables declared but never used), no-console (console.log left in production code), react-hooks/rules-of-hooks (hooks called conditionally — a React runtime error), no-floating-promises (async functions called without await), and @typescript-eslint/no-explicit-any (defeating TypeScript).
ESLint 9 introduced flat config (eslint.config.js) replacing the old .eslintrc format. Flat config is significantly simpler and more performant, resolving the long-standing config cascade confusion.
Popular ESLint plugins: eslint-config-airbnb (32M weekly downloads), @typescript-eslint (TypeScript-specific rules), eslint-plugin-react (React rules including hooks), eslint-plugin-import (import validation), eslint-plugin-security (security vulnerabilities).
ESLint vs Biome: Biome is 25x faster than ESLint (Rust-based) but has fewer rules (350 vs ESLint''s 3,000+) and does not support custom plugins. For maximum rule coverage, ESLint remains the standard.
Key Features
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3,000+ rules: built-in and via plugins for React, TypeScript, imports, security, and a11y
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IDE integration: real-time error highlighting in VS Code, JetBrains, and Neovim
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Autofix: ESLint fixes many rules automatically with --fix flag
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Custom rules: write your own ESLint rules for team-specific patterns
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Flat config: eslint.config.js replaces the complex .eslintrc cascade in ESLint 9+
Pros
- ✓43 million weekly downloads — every JS project template and framework includes ESLint by default
- ✓Catches runtime bugs statically: hooks rules, floating promises, and unused vars before deployment
- ✓3,000+ rules via plugins covering React, TypeScript, security, imports, and accessibility
- ✓Integrates into every IDE with real-time error highlighting as you type
- ✓ESLint 9 flat config is significantly simpler than the old .eslintrc cascade system
Cons
- ✗Can be slow on large codebases — Biome is 25x faster for pure linting performance
- ✗Configuration complexity has historically been a pain point (improved in ESLint 9)
- ✗Rule conflicts between plugins require manual override configuration
Who is using ESLint?
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Every JavaScript and TypeScript developer — ESLint is the standard code quality tool
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React teams who need hooks rule enforcement to prevent subtle bugs
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TypeScript teams who want stricter type safety rules beyond what tsc provides
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Engineering leads who want consistent code style enforced automatically across the team
Use Cases
- →Running ESLint in VS Code to see errors inline as you type before saving
- →Adding ESLint to a CI pipeline to fail PRs that introduce lint errors
- →Configuring react-hooks/exhaustive-deps to catch missing useEffect dependencies
- →Using @typescript-eslint/no-floating-promises to prevent unhandled async errors
Pricing
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Open Source : $0/forever — Full linter, MIT license, Plugin ecosystem, Community support
Pricing details may not be up to date. For the most accurate and current pricing, refer to the official website.
What Makes ESLint Unique?
The JavaScript static analysis tool with 43 million weekly downloads that catches runtime bugs before they reach production — hooks violations, floating promises, and type safety gaps that TypeScript alone misses.
How We Rated It
Download count from npm stats. Rule count from ESLint and plugin documentation. Biome comparison from Biome published benchmarks.
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Accuracy and Reliability 4.6/5
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Ease of Use 4.5/5
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Functionality and Features 4.7/5
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Performance and Speed 4.6/5
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Customer Support 4.5/5
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Value for Money 5.0/5
AI summary
JavaScript and TypeScript linter — 43 million weekly downloads, catches bugs before runtime, configurable rules.