JavaScript Formatter
Beautify or minify JavaScript code online with one click.
Click Format to see the result here
Quick Examples
Click to load an example and try the formatter
About JavaScript Formatter
The JavaScript Formatter supports two modes: Beautify and Minify. Beautify mode automatically adds indentation and line breaks for readability; Minify mode removes all whitespace and comments to produce the smallest possible file size.
This tool runs entirely in the browser — no dependencies, no server uploads. It supports bidirectional conversion: beautified code can be minified again, and minified code can be beautified back.
How to Use
- Paste your JavaScript code into the input area
- Choose Beautify or Minify mode, then click the Format button
- Review the result and click Copy Code to copy to clipboard
Typical Production Scenarios
CI/CD Pipeline Code Style Enforcement
Use the formatter as a quality gate in GitLab CI or GitHub Actions: detect inconsistent style via git diff, auto-beautify, and generate a diff report. For small projects or script libraries, this is lighter than deploying Prettier + ESLint.
Code Review Pre-processing
Beautify PR code with messy indentation before review so diffs focus on logic changes rather than formatting noise. It can also run as part of a pre-commit hook to unify style before every commit.
Third-party Script Security Auditing
Beautify obfuscated or minified third-party SDKs/tracking scripts to inspect suspicious behavior (e.g. accessing document.cookie, sending beacon requests). Formatted code is far more readable, letting security teams review line by line.
Browser Console Snippet Cleanup
Minified JS copied from browser DevTools is often packed into a single line. Paste it here, beautify with one click to understand the logic, modify as needed, re-minify, then paste back into the Console or Tampermonkey.
Inline JS Extraction from Production Logs
Production error logs often contain minified inline JS stack snippets (e.g. code inside onerror attributes). Extract these fragments, beautify them, and cross-reference with source maps to locate the original file — speeding up incident resolution.
Webpack/Vite Bundle Diff Analysis
Pre- and post-bundle JS differ dramatically in size and logical structure. Beautify both versions, then diff them to visually assess tree-shaking effectiveness, module merging patterns, and code-splitting boundaries.
JS Formatting Engine: Boundaries and Tradeoffs
This tool is built on a character-by-character state machine without an AST. This means clear boundaries and tradeoffs when processing JavaScript syntax. Understanding these helps you use the right tool for the right job in production.
Automatic Semicolon Insertion (ASI) Handling
JavaScript automatically inserts semicolons at line breaks, but not all line breaks trigger ASI. The formatting engine preserves semicolon semantics after keywords like return, throw, break, continue, ++, -- to avoid introducing logic changes during formatting. However, it won't add protective semicolons before lines starting with [ or ( — if your code relies on ASI to prevent (function(){})() from being parsed as a function call, inspect these positions after formatting.
Template Literal and Tagged Template Formatting Pitfalls
Whitespace inside template literals is meaningful — indentation and line breaks are part of the string content. The formatting engine never modifies anything inside template literals, including whitespace. If your template literal spans multiple lines with heavy indentation, that indentation stays unchanged after beautification, which may look inconsistent with the surrounding code. Tagged templates (e.g. styled-components' css tag) are equally left untouched to avoid breaking DSL semantics.
Regular Expression Literal Ambiguity
In JavaScript, / serves as both the division operator and the start of a regex literal — a classic ambiguity for character-by-character parsers. This tool uses context-based inference: if / appears in an expression-expected position (after =, (, return), it's treated as a regex start; otherwise, it's division. This covers roughly 95% of real-world cases, but consecutive division expressions like a / b / c may rarely be misjudged. If a regex is formatted incorrectly, rewrite it using the new RegExp() constructor form as a workaround.
Common Mistake Patterns
Expecting the beautifier to fix syntax errors
The formatter performs no syntax validation — if your input has a SyntaxError, your output will too. It only adjusts formatting; it is not a linter. Garbage in, garbage out. Always ensure your code runs correctly before formatting.
Expecting directive comments to survive minification
Minification removes all comments, including directive comments with special semantics (e.g. // @ts-check, // @ts-ignore, // eslint-disable). If you need to preserve these directives, re-add them manually after minification, or protect them with custom markers in a pre-processing step.
Repeated beautify↔minify cycles on inline-regex code
Regex literals containing = (like /=/g, /<=/g) can produce unexpected results such as /= /g or / =/g after repeated beautify↔minify cycles due to whitespace being added then stripped in different positions. Extract complex regexes into variables or use the new RegExp() constructor form before formatting.
Relying on ASI semantics without an explicit use strict directive
When minification removes line breaks, code that depends on ASI (e.g. return followed by a newline returning undefined) may change behavior. Always use strict mode and explicit semicolons — this is the root-cause fix and the standard practice in virtually all production-grade projects.