JavaScript Minifier & Compressor

Every comment, tab stop, and blank line between functions adds bytes that a browser downloads and discards before reading a single instruction. JavaScript Minifier strips them in a single pass without touching your logic. Paste any script and the compressed version appears underneath with a before/after byte count and a progress bar.

JavaScript is harder to compress than CSS because the same character can mean three different things depending on context: a / after a closing parenthesis is division, after = it opens a regex literal, and after console.log it starts nothing at all. The scanner tracks the last non-whitespace token to decide, keeping string contents and regex bodies inside sentinels no later pass sees.

Worked Example: Compressing the greet Function

Press Load Sample and the first script loaded is:

function greet(name) {
  console.log("Hi, " + name);
  return name.length;
}
greet("Aria");

With default options the output is:

function greet(name){console.log("Hi, "+name);return name.length;}greet("Aria");

Indentation, the blank line between the function body and the call, and spaces around the + operators are removed. The string content "Hi, " is untouched because the quotes place it behind a sentinel before any space pass runs.

What Each Option Controls

• Strip comments (default on) removes all // and /* */ comments. A /*! licence banner is always preserved regardless, so attribution stays attached to the minified file.
• Collapse spaces removes indentation, blank lines and optional whitespace around punctuation. Turn it off when comparing two outputs: comments are still stripped but line structure stays readable.
• Shorten booleans replaces bare true with !0 and bare false with !1. Both evaluate identically in every JavaScript engine. Leave it off for debug builds.
• Drop console.* removes every console.log, console.warn, console.error and similar call, arguments included, and reports how many were removed under the output.

Edge Cases and Tricky Inputs

• Template literals keep all their whitespace, including deliberate newlines inside multi-line strings. Expression slots ${…} are scanned for their closing brace but their contents are not rewritten.
• Regex literals are protected once the scanner decides the / is not division. A character class like [^/\n] containing a forward slash does not end the pattern early because the scanner tracks whether it is inside […].
• Unterminated strings stop the minifier entirely and show the message "A double-quoted string cannot span multiple lines." This prevents a partially minified file that silently breaks at runtime.
• Comment-only input compresses to 0 bytes. The byte counter reads 0 B after and 100.0% saved, which is correct: a file the browser never needs to parse costs nothing to deliver.