JSON Formatter
Pretty-print, validate and minify JSON — securely in your browser.
About this tool
Paste any JSON, get it formatted, validated and syntax-highlighted instantly. Collapse nested objects, find errors with line-level feedback, and copy pretty or minified output.
How it works
The tool uses JSON.parse with a position-tracking wrapper that surfaces precise error locations, then re-serialises with JSON.stringify(indent) for pretty output. Syntax highlighting is a lightweight tokeniser, not a heavy library.
How to use JSON Formatter
- 1Paste or type JSON into the input area.
- 2Fix any validation errors flagged inline — the tool highlights the problem location.
- 3Use the formatting buttons: pretty (2-space) or minified.
- 4Collapse nested objects and arrays, then copy or download the result.
Examples
Pretty-printing a minified API response makes it readable in seconds.
A missing comma is flagged with the exact line so you can fix it.
Minifying a config file trims whitespace for smaller payloads.
Pro tips
- Use the sample button to load a realistic example if you just want to explore.
- Collapsed nodes keep huge payloads manageable — expand only what you need.
- The validation is identical to a full parser: if it passes here, it is valid JSON.
Frequently asked questions
What makes JSON invalid?
Trailing commas, unquoted keys, single-quoted strings and comments are the most common issues. The tool points at the first problem.
Is my data sent to a server?
No. All parsing and formatting happens in your browser. JSON Formatter is fully offline-capable.
Can I use it for large files?
Yes, for files in the tens of megabytes range it stays responsive thanks to a streaming tokeniser. Extremely large files may be slow in older browsers.
Advertisement
