JSON Formatter & Validator
Validate and pretty-print JSON with custom indentation. Everything happens locally.
Paste minified or malformed JSON and get it validated and pretty-printed with your choice of indentation, or catch a syntax error with its exact location highlighted. Useful for debugging an API response that came back as one long line, cleaning up a config file, or checking whether a payload is valid JSON before sending it. Formatting and validation both run locally with no upload.
Runs on your device. This tool processes your file inside this browser tab. Nothing is uploaded, so it also works offline once the page has loaded, and closing the tab discards the file from memory.
Loading tool
How it works
- 01
Paste your JSON.
- 02
Choose an indentation style.
- 03
Copy the formatted, validated output.
Details
- Category
- Developer & data
- Formats
- JSON
- Runs
- In your browser
- Files uploaded
- No
- Cost per run
- Free
- Sign-in
- Not required
- Works offline
- Yes, once loaded
Last updated 2026-08-12
Common questions
What happens if my JSON is invalid?
The formatter highlights the exact position of the parse error so you can find and fix it quickly.
Can I choose the indentation size?
Yes - pick 2 spaces, 4 spaces, or tabs for the pretty-printed output.
Can I minify JSON with this too?
Yes - collapsing to a single line with no whitespace is one of the formatting options.
Does it upload my JSON?
No - validation and formatting happen locally.
Use this from your code
This tool is also a REST endpoint, so you can run it in a pipeline instead of by hand. It is free and needs no API key. See the API reference for every parameter.
curl -X POST https://fileoven.com/api/v1/tools/json-formatter \
-H "Content-Type: application/json" \
-d '{"json":"{\"id\":1,\"name\":\"Ada\"}"}'