JSON Formatter & Validator
Pretty-print, minify and validate JSON. Parsing happens locally.
How to format, validate or minify JSON
- Paste your JSON. Paste or type it into the editor.
- Format or minify. Click "Format" to pretty-print with 2, 4 or 8-space indentation, or "Minify" to strip it down to one line.
- Validate and save. Click "Validate" to check syntax and see a key count, then copy or download the result.
What happens to your data
Formatting, minifying and validating all run in your browser using standard JavaScript JSON parsing — nothing you paste is sent to OpenToolkit or any server.
There's no fixed size limit, but a very large document (many megabytes) can slow down the editor since parsing and rendering both happen in the same browser tab.
What this formatter supports
Common reasons to format JSON
- Pretty-print a minified API response to actually read it.
- Shrink a config file down before embedding it somewhere space-constrained.
- Track down a missing comma or bracket via the validator's error message.
- Turn a single-line payload into something reviewable in a pull request.
Frequently asked questions
Is my JSON uploaded anywhere?
No. Parsing, formatting and validation all happen in your browser tab; nothing you paste is sent to OpenToolkit.
Is there a size limit?
No fixed limit, but very large documents can make the editor feel slower since everything runs in one browser tab.
What happens if my JSON is invalid?
Validate reports the syntax problem so you can find and fix it, rather than failing silently.
Can I go from JSON to YAML?
Not here — but the YAML Editor converts YAML to JSON, which covers the reverse direction.
Does formatting change my data?
No — formatting and minifying only change whitespace and indentation; the keys and values themselves are untouched.
Can I download the result?
Yes — copy it to your clipboard, or download it as a .json file.
Last reviewed: August 2026