JavaScript Compressor Free Online Tool 2026

Last updated March 22, 2026

Example: Variable Name Mangling

// Before:
function processUserAuthentication(userCredentials, authenticationConfig) {
  const hashedPassword = hashFunction(userCredentials.password);
  const isValidUser = checkDatabase(userCredentials.username, hashedPassword);
  const sessionToken = generateToken(authenticationConfig.secretKey);
  return { isValidUser, sessionToken };
}

// After (with mangling):
function processUserAuthentication(a,b){const c=hashFunction(a.password),d=checkDatabase(a.username,c),e=generateToken(b.secretKey);return{isValidUser:d,sessionToken:e}}

Example: Dead Code Elimination

// Before (with dead code):
function getEnvironment() {
  const env = 'production';
  
  if (false) {
    console.log('This never runs');
    return 'debug';
  }
  
  if (env === 'development') {
    return 'dev';  // unreachable — env is always 'production'
  }
  
  return env;
}

// After (dead code removed):
function getEnvironment(){return"production"}

Example: Constant Folding

// Before:
const SECONDS_PER_MINUTE = 60;
const MINUTES_PER_HOUR = 60;
const HOURS_PER_DAY = 24;
const SECONDS_PER_DAY = SECONDS_PER_MINUTE * MINUTES_PER_HOUR * HOURS_PER_DAY;
const MS_PER_DAY = SECONDS_PER_DAY * 1000;

// After (constants folded at compile time):
const MS_PER_DAY=86400000;

Example: Comment Stripping

// Before (with comments, 580 bytes):
/**
 * Validates an email address format.
 * @param {string} email - The email to validate
 * @returns {boolean} True if valid, false otherwise
 */
function isValidEmail(email) {
  // RFC 5322 compliant regex
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  
  // Check if email is a string
  if (typeof email !== 'string') {
    return false;
  }
  
  // Test against regex
  return emailRegex.test(email.toLowerCase());
}

// After (comments stripped, 121 bytes):
function isValidEmail(e){return typeof e==="string"&&/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(e.toLowerCase())}

Example: License Comment Preservation

// Before:
/*!
 * MyLibrary v2.1.0
 * (c) 2024 Example Corp
 * Released under the MIT License
 */

// Regular comment — will be removed
function add(a, b) {
  return a + b;
}

// After (license comment preserved):
/*!
 * MyLibrary v2.1.0
 * (c) 2024 Example Corp
 * Released under the MIT License
 */
function add(a,b){return a+b}

File: app.js

Original size:        245,820 bytes (240 KB)
After whitespace:     178,340 bytes (174 KB) — 27% reduction
After comments:       165,210 bytes (161 KB) — 33% reduction
After mangling:       142,880 bytes (140 KB) — 42% reduction
After dead code:      138,450 bytes (135 KB) — 44% reduction
Final minified:       138,450 bytes (135 KB) — 44% reduction

Estimated gzip:        42,300 bytes (41 KB)  — 83% reduction
Estimated brotli:      36,100 bytes (35 KB)  — 85% reduction

// Minified output (app.min.js):
function a(b,c){if(c<0||c>100)throw new Error("Invalid");return b*(1-c/100)}
//# sourceMappingURL=app.min.js.map

// Source map (app.min.js.map) maps back to original:
{
  "version": 3,
  "sources": ["app.js"],
  "names": ["calculateDiscount", "price", "discountPercent"],
  "mappings": "AAAA,SAASA,kBAAkBC,EAAOC..."
}

// In browser DevTools, the debugger shows the original:
function calculateDiscount(price, discountPercent) {
  if (discountPercent < 0 || discountPercent > 100) throw new Error("Invalid");
  return price * (1 - discountPercent / 100);
}

Batch Compression Results

Processing 5 files...

File                  Original    Minified    Savings
app.js                240 KB      135 KB      44%
vendor.js             820 KB      410 KB      50%
utils.js               45 KB       22 KB      51%
components.js         180 KB       98 KB      46%
router.js              28 KB       14 KB      50%

Total                1,313 KB     679 KB      48%
Estimated gzip         390 KB     195 KB      50%

Paste your JavaScript code or upload a file to compress it. The compressor preserves all functionality while achieving the maximum possible size reduction for faster page loads.

// Before (formatted, 312 bytes):
function calculateDiscount(price, discountPercent) {
  if (discountPercent < 0 || discountPercent > 100) {
    throw new Error('Discount must be between 0 and 100');
  }
  const discountAmount = price * (discountPercent / 100);
  const finalPrice = price - discountAmount;
  return Math.round(finalPrice * 100) / 100;
}

// After (minified, 148 bytes — 53% reduction):
function calculateDiscount(e,t){if(t<0||t>100)throw new Error("Discount must be between 0 and 100");return Math.round((e-e*(t/100))*100)/100}

// Before (ES6+):
const greet = (name = 'World') => `Hello, ${name}!`;
const users = ['Alice', 'Bob', 'Charlie'];
const greetings = users.map(greet);

// After (transpiled to ES5 + minified):
var greet=function(n){return"Hello, "+(n===void 0?"World":n)+"!"};var greetings=["Alice","Bob","Charlie"].map(greet);