Free Online JavaScript Tools
Beautify, format, and validate JavaScript and JSON5 online. All 14 tools run client-side — your data stays private.
Beautify and format JavaScript code with proper indentation.
Pretty print JavaScript for improved readability.
Format JSON5 files including comments and relaxed syntax.
Validate JSON5 syntax with detailed error reporting.
Format Babel-transpiled JavaScript output for readable debugging.
Format JavaScript with Flow type annotations.
Format TypeScript with type annotations and generic spacing.
Generate Flow type alias from JSON sample data.
Generate React PropTypes from JSON shape.
Strip whitespace and comments to shrink JavaScript bundles.
Format React JSX with proper indent and prop alignment.
Format TypeScript JSX with type annotations preserved.
Minify JSX while keeping the React tree intact.
Migrate JSX components to TypeScript TSX with type stubs.
What Are Online JavaScript Tools?
Our JavaScript tools help developers format and validate JavaScript code and its related formats. This includes beautifying compressed JS, pretty-printing code for review, and working with JSON5 — a superset of JSON that adds comments, trailing commas, and more relaxed syntax for config files.
All tools run in the browser with no installation required — perfect for quick formatting tasks during code review, debugging, or documentation work.
Common Use Cases
- check_circleBeautify minified JavaScript from a CDN or bundle output
- check_circlePretty-print JS code for inclusion in documentation or blog posts
- check_circleFormat JSON5 config files with comments for readability
- check_circleValidate JSON5 syntax before using it in a Node.js application
- check_circleClean up auto-generated JavaScript from a code generator
- check_circleFormat inline scripts embedded in HTML files
Frequently Asked Questions
What is JSON5 and how does it differ from JSON?
JSON5 is a superset of JSON that adds support for comments, trailing commas, unquoted object keys, single-quoted strings, and multi-line strings — making it more suitable for human-authored config files.
Is JSON5 supported natively in browsers?
No. JSON5 is not natively supported by browsers or the standard JSON.parse() method. You need the json5 npm package or a build-time parser to use JSON5 in applications.
What is the difference between JS Beautifier and Pretty Print?
Both format JavaScript code for readability. JS Beautifier offers more options for controlling indentation style, brace placement, and line length. Pretty Print applies straightforward indentation with sensible defaults.
Can I format TypeScript with these tools?
For TypeScript-specific formatting with type annotation support, use our dedicated TypeScript Formatter available in the Formatters section.
Developer Insights
From the Blog
URL Encoding in JavaScript: encodeURI vs encodeURIComponent
A practical guide to the four URL encoding functions in JavaScript with real code examples.
Common URL Encoding Mistakes and How to Avoid Them
Double encoding, encoding full URLs, mixing + and %20 — subtle bugs that only appear in production.
The Case for 100% Client-Side Data Processing
Why we built OpenFormatter to process all data locally, and what that means for your workflow security.