JS Beautifier — Pretty-Print and Format JavaScript Online
🔒 Runs in your browser — nothing is sent to a serverJS beautifier that pretty-prints, unminifies and formats any compressed or one-line JavaScript bundle into a readable structure with proper indentation. Paste a Webpack output, a CDN-served library, a Terser-minified entry chunk or a copy-pasted snippet from DevTools, and this JavaScript formatter parses the source, places each statement on its own line with a configurable 2-space, 4-space or tab indent, and applies your preferred K&R, Allman or Stroustrup brace style. Comments, JSDoc, template literals and regex literals are preserved verbatim. Quote style and semicolon presence are kept exactly as in the source. Everything runs 100% inside your browser; your input never leaves your device, nothing is uploaded, logged or sent to any server.
Comments, JSDoc, template literals and regex literals are preserved verbatim. Quote style and semicolon presence are kept exactly as in the source.
When to use a JavaScript beautifier online
You reach for a JS beautifier any time a production bundle, a CDN-served library or a Terser-minified entry chunk arrives unreadable: debugging a third-party error in a stack trace that points at column 17321, reverse-engineering an obscure helper, walking through a webhook payload that ships its own glue script, comparing two builds in a code-review diff, or preparing a one-liner from DevTools for inclusion in documentation. Browser-local beautifying matters when the source contains internal admin logic, customer-side secrets baked into the bundle or unreleased product features — the script never travels to a remote SaaS formatter.
How JavaScript pretty-printing works under the hood
JavaScript pretty-printing is an AST-driven pipeline. The `js-beautify` tokenizer reads the source character by character, distinguishing operators from regex literals via grammar context (the lexer needs to know whether a `/` follows an expression or a statement), recognising template literals as opaque opaque-text tokens, and passing comments through with their original position. The renderer walks the resulting token stream, places each statement on its own line at the configured indent, applies your brace style, optionally wraps long expressions at the chosen line length and emits the formatted output. Behaviour is preserved exactly: every identifier, every literal, every operator survives untouched.
Examples
function add(a,b){return a+b}const sum=add(1,2);if(sum>0){console.log("positive",sum)}else{console.log("zero or negative")}function add(a, b) {
return a + b
}
const sum = add(1, 2);
if (sum > 0) {
console.log("positive", sum)
} else {
console.log("zero or negative")
}
const greet=(user)=>`Hello, ${user?.name??"stranger"}!`;const users=[{name:"Alice"},{name:"Bob"},{}];users.map(greet).forEach((m)=>console.log(m));const greet = (user) => `Hello, ${user?.name??"stranger"}!`;
const users = [{
name: "Alice"
}, {
name: "Bob"
}, {}];
users.map(greet).forEach((m) => console.log(m));
const tool="js beautifier";const useCase="format minified JavaScript";export const meta={tool,useCase,online:true};const tool = "js beautifier";
const useCase = "format minified JavaScript";
export const meta = {
tool,
useCase,
online: true
};
/** Render a greeting card.
* @param {string} name
* @returns {string} HTML
*/
function render(name){return `<div class="card">Hello, ${name}!</div>`}/** Render a greeting card.
* @param {string} name
* @returns {string} HTML
*/
function render(name) {
return `<div class="card">Hello, ${name}!</div>`
}