JavaScript Minifier
Minify and compress JavaScript code to reduce file size
JavaScript Minifier
Compress and optimize your JavaScript code by removing whitespace, comments, and unnecessary characters
Minification Options
Privacy: All JavaScript minification happens in your browser. No data is sent to any server.
Your Privacy is Protected
All processing happens entirely in your browser. No data is stored, transmitted, or tracked. Your information remains completely private and secure on your device.
About JavaScript Minifier
A JavaScript minifier is a critical web performance optimization tool that compresses JavaScript code by removing all unnecessary characters, whitespace, comments, and reducing code syntax to its most compact form without changing functionality. Minification can reduce JavaScript file sizes by 40-70%, significantly improving website load times, bandwidth usage, and Core Web Vitals scores. The process removes spaces, line breaks, indentation, and comments that developers need for readability but browsers don't need to execute code. Advanced minifiers also perform code transformations like shortening variable names, simplifying expressions, removing dead code, and optimizing syntax patterns. Our JavaScript minifier handles modern ES6+ syntax, preserves code functionality while achieving maximum compression, and provides detailed statistics on compression ratios. For production websites, serving minified JavaScript is essential—faster downloads mean better user experience, improved mobile performance, lower hosting costs, and better search engine rankings. The minifier maintains a source map linking minified code back to original code for debugging, ensuring you can develop with readable code while serving optimized code to users. Whether you're optimizing a single script or an entire application, JavaScript minification is a fundamental performance optimization that every web developer should implement.
Key Features
Maximum Compression
Removes all unnecessary whitespace, line breaks, indentation, and comments to achieve the smallest possible file size. The minifier analyzes every character and removes anything that doesn't affect code execution, typically reducing file sizes by 40-70%.
Variable Name Shortening
Renames local variables to shorter names (a, b, c, etc.) while preserving functionality. This significantly reduces file size for code with long descriptive variable names, but only affects local variables—global variables and properties remain unchanged to prevent breaking code.
Dead Code Elimination
Identifies and removes unreachable code, unused functions, and redundant expressions. If code can never execute (like statements after a return), or functions are never called, the minifier removes them, further reducing file size and improving execution performance.
Expression Optimization
Simplifies JavaScript expressions and statements where possible. For example, converts 'true === x' to 'x', simplifies boolean logic, and optimizes mathematical expressions. These micro-optimizations accumulate for substantial size reduction.
ES6+ Syntax Support
Fully supports modern JavaScript including arrow functions, template literals, destructuring, spread operators, async/await, classes, modules, and all ES2015-ES2023 features. Minifies modern syntax correctly while maintaining functionality.
Source Map Generation
Generates source maps that link minified code back to original source code. When debugging minified code in production, source maps allow browser dev tools to display original readable code, making production debugging possible without serving unminified files.
Compression Statistics
View detailed statistics showing original file size, minified size, bytes saved, percentage reduction, and estimated load time savings. Quantify the performance impact of minification and track optimization progress across your codebase.
Safe Minification Modes
Choose between aggressive optimization (maximum compression, may be harder to debug) and safe optimization (conservative approach that's easier to debug if issues arise). Safe mode preserves more structure while still achieving significant compression.
How to Use the JavaScript Minifier
Paste your JavaScript code into the input editor
You can paste code from your development files, libraries, or any JavaScript you want to optimize for production deployment.
Choose your minification level
Select 'Standard' for balanced compression and debuggability, or 'Aggressive' for maximum file size reduction with more extensive code transformations and optimizations.
Enable optional advanced features if needed:
Enable optional advanced features if needed: variable name mangling (rename variables to shorter names), dead code removal (eliminate unreachable code), or source map generation (for production debugging).
Click 'Minify JavaScript' to compress your code
The tool processes your input using advanced algorithms and displays the minified result with comprehensive compression statistics.
Review compression statistics to see original size, minified size, bytes saved, and percentage reduction
This helps you understand the performance impact and quantify the optimization benefit.
Copy the minified JavaScript to your clipboard or download it as a .min.js file ready for production deployment
If you generated a source map, download that as well for production debugging.
Replace your production JavaScript files with minified versions
Keep original formatted source files for development and future maintenance. Never edit minified code directly—always modify source files and re-minify.
Test your website thoroughly after deploying minified code to ensure all functionality works correctly
While minification is safe, testing verifies that everything executes as expected in production.
Frequently Asked Questions
Will minifying break my JavaScript?
Modern minifiers are extremely safe and rarely break code when used correctly. They only remove elements that don't affect execution and perform safe code transformations. However, if your code has syntax errors, relies on specific variable names, or uses eval() improperly, issues can occur. Always test thoroughly after minification. Use safe mode for conservative optimization if you experience problems.
How much does minification improve performance?
Minification typically reduces JavaScript file sizes by 40-70%, directly improving load times. For a 200KB JavaScript file, you might save 100-140KB. On a 3G connection, this could save 400-800ms of load time. Combined with gzip/brotli compression, total size reduction can reach 80-90% compared to original formatted code, dramatically improving performance.
Should I minify during development?
No, never develop with minified code. Keep your source JavaScript files beautifully formatted with descriptive variable names, comments, and proper indentation for readability and maintenance. Only minify when building for production. Use build tools to automatically create minified versions from source files, maintaining both readable and optimized versions.
What are source maps and do I need them?
Source maps link minified production code back to original source code. When debugging production issues, browser dev tools use source maps to display original code instead of minified code, making debugging possible. You should generate source maps and deploy them to production (they only download when dev tools are open), allowing you to debug production issues effectively.
Can I reverse minification?
Partially. You can beautify minified code to add formatting back, but you'll lose comments, original variable names (if mangled), and any removed dead code. This is why maintaining source files is critical. Never edit minified code—always make changes to source files and re-minify. Use version control to track source files, not minified versions.
What's the difference between minification and compression?
Minification removes unnecessary code and optimizes syntax at the source code level. Compression (gzip/brotli) is applied by servers during file transfer, temporarily making files smaller during transmission. They work together: minify JavaScript files first, then let your server compress them during delivery. Combined, you achieve 80-90% size reduction compared to original files.
Should I minify third-party libraries?
Most reputable libraries provide pre-minified versions (filename.min.js). Use these instead of minifying yourself—they're already optimized. If a library only provides source code, you can minify it, but check licenses first. For your own code and code you control, always minify for production.
How does minification affect debugging?
Minified code is very difficult to debug without source maps because variable names are shortened, formatting is removed, and everything is on one line. With source maps, browser dev tools show original code even when minified code is executing, making debugging feasible. Deploy source maps to production, or keep them internal if security is a concern.
Use Cases
- Production Website Optimization: Optimize JavaScript files before deploying websites to production servers. Minified scripts load faster, improving initial page load time, Time to Interactive, and overall user experience. Essential for any public-facing website, especially those with large JavaScript bundles or multiple scripts.
- Mobile Performance Enhancement: Reduce JavaScript file sizes for better mobile performance on bandwidth-constrained networks. Smaller files mean faster downloads on 3G/4G connections, lower data usage for users, and improved mobile Core Web Vitals metrics that affect mobile search rankings and user satisfaction.
- CDN and Hosting Cost Reduction: Lower CDN bandwidth costs and hosting expenses by serving smaller files. If you pay for data transfer, minified JavaScript can significantly reduce costs. Even 50KB savings per file multiplied by millions of visitors results in substantial bandwidth and cost savings over time.
- Single Page Application (SPA) Optimization: Reduce bundle sizes for React, Vue, Angular, or other SPA frameworks. Large JavaScript bundles are a common performance bottleneck in SPAs. Minification combined with code splitting and tree shaking dramatically improves initial load time and time to interactive.
- Build Pipeline Integration: Integrate JavaScript minification into automated build processes with Webpack, Rollup, Gulp, or Grunt. Minify automatically during production builds while keeping development code readable. This ensures optimal performance without manual minification for every release.