JSON Formatter / Validator
Format and validate JSON — with the error pinned to a line and column.
How this reads your output
The tool parses your JSON with the browser’s built-in engine. If it is valid, it pretty-prints it with two-space indentation and reports the key count, nesting depth and minified size. If it is not, it turns the parser’s character position into a line and column and quotes the text around the error — so you can find it in a large file instead of hunting.
What the results mean
- Line and column
- Where the parser gave up. The real mistake is often just before this point — a missing comma on the previous line, for instance.
- Max depth
- How deeply the structure nests. Very deep JSON is harder to work with and sometimes a sign of a data-modelling problem.
- Minified size
- The JSON with all whitespace removed. Useful when you need to know the payload size for an API.
Common problems and fixes
- My JSON is rejected but it looks fine
- The usual culprits are a trailing comma after the last item, a comment (JSON has none), or single quotes instead of double. All are valid JavaScript but invalid JSON.
- The error points at a line that looks correct
- A JSON parser reports where it could not continue, which is often just after the real mistake. Check the line before the reported position for a missing comma or bracket.
Frequently asked questions
Why is my JSON with comments invalid?
The JSON standard does not allow comments — that was a deliberate design decision. Some tools accept a "JSONC" variant with comments, but strict JSON, which is what APIs expect, does not. Remove them, or the file will be rejected by any conforming parser.
Is my data sent to a server?
No. Parsing uses the browser’s own JSON engine and runs entirely on your device. Open your network panel while formatting and you will see no request carrying your data.