JavaScript CSS Minifier Tool - Free Online Code Minification and Compression

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Free JavaScript and CSS Minifier Tool with instant browser-based compression. All minification processes are performed entirely within your browser - during the use of this tool, your code never leaves your device or gets uploaded to any server.

⚠️ IMPORTANT DISCLAIMER:

  • This tool is provided for demonstration purposes only, "AS IS" without any warranties.
  • We accept NO responsibility for code loss, functionality issues, or minification errors.
  • Always keep secure backups of your original source code before minification.
  • The minified code may not work identically to the original in all environments.
  • Test thoroughly after minification - edge cases and compatibility issues may occur.
  • DO NOT use this tool for critical production code without extensive testing and verification.
  • Minification parameters can affect code behavior - understand the options before changing them.
  • By using this tool, you accept FULL responsibility for all outcomes and consequences.

Privacy & Security: This tool operates entirely within your browser using client-side JavaScript. During the minification process, no code is transmitted to servers, and all processing happens locally on your device. Even if our website goes offline, the tool will continue to work once loaded. However, functionality depends entirely on your browser compatibility and device performance. What you do with the minified code after using this tool is your responsibility.

ℹ️ Note: Modify the JavaScript object above to customize minification behavior. You can use comments and multi-line format. View Terser documentation for available options.

Features:

  • 🚀 Fast Minification: Uses Terser for JavaScript and industry-standard algorithms for CSS
  • 🖥️ Client-Side Processing: All operations performed locally in your browser
  • 📝 JS & CSS Support: Minify both JavaScript and CSS code
  • 🔍 Auto Detection: Automatically detects code language
  • ⚙️ Customizable JS Options: Configure Terser parameters for JavaScript minification
  • 📱 Mobile Friendly: Responsive design works on all devices
  • 🔒 No Data Transmission: Your code never leaves your device
  • 💾 File Download: Download minified files directly
  • 📊 Compression Stats: See size reduction statistics

How to Use:

  1. Paste your JavaScript or CSS code into the left text area
  2. The tool will automatically detect the language and select the appropriate radio button
  3. If auto-detection fails, manually select JavaScript or CSS
  4. For JavaScript: Review and adjust Terser parameters if needed
  5. Click the "Minify" button to compress your code
  6. The minified result appears in the right text area
  7. Use "Copy Result" to copy to clipboard or "Download" to save as file
  8. Important: Always test the minified code thoroughly before deployment

Benefits of Code Minification:

  • Faster Load Times: Reduce file size for quicker downloads
  • Bandwidth Savings: Less data transfer means lower costs
  • Better Performance: Smaller files improve website performance
  • Production Ready: Optimize code for deployment

Best Practices & Warnings:

  • Always Backup: Keep original source code in version control or secure storage
  • Test Thoroughly: Minified code should be tested in all target environments
  • Understand Parameters: Aggressive minification can break code functionality
  • Check Compatibility: Ensure minified code works across browsers and platforms
  • Use Source Maps: Consider generating source maps for production debugging
  • Verify Output: Review critical functionality after minification

Based on Third-Party Libraries

Terser (JavaScript Minifier)
Copyright 2012-2018 (c) Mihai Bazon
Licensed under BSD-2-Clause License.
GitHub Repository

CSS Minifier (Based on Minify - Adapted and Modified)
Based on Minify by Matthias Mullie
Original: GitHub Repository
Original Copyright (c) 2012, Matthias Mullie. All rights reserved.

Adapted from PHP to JavaScript and modified by Hidekazu Konishi, 2025.
Licensed under MIT License.

View Original MIT License 
Copyright (c) 2012 Matthias Mullie

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

References:
Tech Blog with curated related content
Web Tools Collection

Written by Hidekazu Konishi