A snippet pasted from a bundle, a gist, or a Stack Overflow answer is unreadable until it has been formatted, and reading unfamiliar code is hard enough without fighting the whitespace.
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JS Formatter
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Free · API · MCPToolYour platform
Use JS Formatter three ways
The free JS Formatter on this page works in your browser. The same workflow is available via REST API for apps and via MCP for Cursor, Claude, and other agents — one API key, one plan, one quota. This tool is part of the developer-apis module under Developer Tools.
- Free in browserUse JS Formatter here — no account required.
- REST APICall from your server with
X-Api-Key. - MCP for agentsConnect Cursor or Claude to ToolYour MCP with the same key.
- 1. Get an API keySign in and open Dashboard → API Keys (works for REST and MCP).
- 2. Call or connectUse the REST API from your server, or paste the MCP URL into your agent config.
- 3. Same qualityOutput matches the free web tool across all three surfaces.
What is JS Formatter?
A snippet pasted from a bundle, a gist, or a Stack Overflow answer is unreadable until it has been formatted, and reading unfamiliar code is hard enough without fighting the whitespace. This JS formatter runs Prettier with the babel parser at a hundred-character print width, applying consistent indentation, quoting, semicolons, and line breaking.
Parsing comes first, which makes formatting a free syntax check: if the code will not parse, you get the error and its position rather than partially formatted output. Babel handles modern JavaScript and JSX. What this does not do is apply your project's ESLint rules, resolve imports, transpile, or type-check — it is a printer, not a build step, and a TypeScript project is still better served by your editor with its own configuration. When you want the opposite direction, JS Minifier strips the whitespace back out and reports the byte saving.
Browser use is free and needs no signup. The same job runs over REST at POST https://api.toolyour.com/api/v1/developer-apis/js-formatter and over MCP at https://api.toolyour.com/mcp — one API key, one shared monthly credit pool, 1 credit per successful call.
What are common questions about JS Formatter?
Does it handle TypeScript?
The babel parser covers modern JavaScript and JSX well. For a TypeScript project, use your editor so the project's own Prettier and ESLint configuration applies.
Does it fix lint problems?
No. Formatting changes whitespace and punctuation, not logic. Unused variables and other rule violations need ESLint.
What happens with a syntax error?
You get the parser error and its location, and no output. A failed format is usually the fastest way to find a missing bracket.
What are the key features of JS Formatter?
Prettier with babel
Modern syntax and JSX print correctly at a readable hundred-character width.
Formatting doubles as a syntax check
Code that will not parse reports the error rather than producing half-formatted output.
Consistent everywhere
Browser, REST, and MCP all run the same formatter, so output does not drift between contexts.
How do you use JS Formatter?
Paste the JavaScript
A minified fragment, an unfamiliar snippet, or generated output.
Format and read
Follow the control flow once the structure is visible.
Adopt or discard
Bring the formatted version into your editor, where project rules take over.
Reading code you did not write
Formatting is the cheapest first step when auditing an unfamiliar snippet, and there is a security angle. Obfuscated or malicious JavaScript relies on being unreadable — long single lines, dense ternaries, and hex-escaped strings. Once formatted, the structure of what it does becomes apparent even when identifiers are meaningless.
Look specifically for network calls to unexpected hosts, dynamic evaluation, and long encoded string constants. Formatting does not decode those, but it shows you where they are, which is the difference between an audit and a scroll.
Format, then measure
The two JavaScript tools here are deliberate opposites. Format for reading and reviewing; minify with JS Minifier to compare sizes. Running a snippet through both shows how much of a file is whitespace and comments, which is a useful sanity check when a bundle looks larger than expected.
For production builds, keep using esbuild, Terser, or your bundler — they perform real transformations such as dead-code elimination and identifier mangling that a lightweight pass cannot. If the script is embedded in a page, HTML Formatter makes the surrounding document readable too.
Which formatter and utility tools sit in this cluster?
Where do you browse more developer tools tools?
- Developer Tools tools
Browse the full Developer Tools category on ToolYour.
- Marketing Tools tools
Build UTM links, check ads copy limits, QA email subjects, and calculate ROAS/CPC/CTR — free in the browser; R
- Security Tools tools
Check HTTP security headers, TLS, cookies, JWTs, passwords, hashes, and SPF/DKIM/DMARC — free in the browser;
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