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Developer · Local utility

JavaScript Formatter

Format JavaScript with a real parser in a local Worker — read untrusted code without executing it, at a two- or four-space indent.

Task path / input to outcome

Paste your JavaScript

Runs locally · Nothing is uploaded

How JavaScript Formatter works, privacy, and related tools

Task path / input to outcome

How to format JavaScript

  1. 01

    Paste your JavaScript

    Paste source up to 256 KiB UTF-8. Select two or four spaces for formatting.

  2. 02

    Choose the indentation

    Choose 2 or 4 spaces. The sample is preloaded; the new setting takes effect when you press Format.

  3. 03

    Format without executing

    Press Format. Prettier parses and reprints JavaScript with the chosen indentation and a 100-column print width without executing it; run your tests.

  4. 04

    Review the result and statistics

    Compare UTF-8 input and output bytes and the savings percentage. A negative saving means the result grew; inspect it before copying or downloading.

  5. 05

    Copy or download the result

    Copy result sends the formatted code to the clipboard; Download saves it as toolars.js. Reset clears the input, output, and options when you are ready for the next snippet.

Tool facts

Processing
In your browser
Input leaves this device
Never
Retention
Nothing is stored
Price
Free

Your input stays in the browser.

JavaScript Formatter uses its verified local execution path and does not create a hidden input or output history.

Local execution

Runs inside the current browser tab.

No hidden processing

Active tool data never becomes a Toolars document record.

No account required

Use the core workflow without creating a profile. Favorites sync to your account after you sign in.

Immediate reset

Clear the tab and the active working data is gone.

When JavaScript Formatter is useful

Code reviews

Make source easier to inspect before sharing it with another developer.

Build artifacts

Create compact HTML, CSS, or JavaScript without executing the source.

Copy-ready snippets

Format a focused example and move it directly into documentation or an editor.

What JavaScript Formatter actually does

A stack-trace snippet from production has to be read before a hotfix can be written, and it arrives as one long line. A bookmarklet found on a forum should be inspected before it earns any trust, and a colleague's clever one-liner needs to become code the team can maintain. JavaScript Formatter parses and re-indents the source without executing it, entirely on the device, with the indentation width your project already uses. That is exactly how untrusted code should be handled: read first, run never — unless you later choose to.

Common questions

What is the size limit?
Input is limited to 256 KiB and output to 512 KiB. The local Worker has separate five-second startup and run budgets; editing or Cancel stops it.
Does formatting run my code?
No. The formatter parses JavaScript to print it with consistent indentation; it does not evaluate expressions or call functions. A successfully formatted file still needs the project’s own tests.
Why does the formatter reject my snippet?
The parser expects syntactically valid JavaScript. A truncated paste, an unbalanced bracket, or a stray character stops the run, and the error names the line and column; fix the syntax and run it again. Nothing partial is emitted from invalid input.
Can I choose tabs or another indent width?
No. Indent size is limited to 2 spaces or 4 spaces, the two widths most JavaScript projects standardize on. For anything else, format here and let the project's own tooling, such as its editor config, apply the final convention.
What does the statistics row tell me?
This row reports UTF-8 bytes before and after transformation and their difference. Formatting may increase size; the figure says nothing about validity or visual equivalence.
Is my code uploaded anywhere?
No. Source is parsed inside a local Worker and is never executed, uploaded or saved. Parser acceptance is not application correctness or browser compatibility.

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