JSON formatter & validator
Paste JSON from an API response, config file, or log line to validate syntax, pretty-print with readable indentation, or minify for production.
How to format and validate JSON
1. Paste raw JSON into the input area (or a fragment wrapped if needed).
2. Click format to pretty-print with standard 2-space indent, or minify for one line.
3. Fix any validation error the parser reports — often a trailing comma or single quotes.
4. Copy the cleaned output into your IDE, Postman, or deployment config.
JSON formatting examples
Pretty-print API response
Minified `{"id":42,"name":"Ada","roles":["admin","user"]}` becomes indented multi-line JSON for readable diffs in code review.
Catch invalid JSON
`{"status": "ok",}` fails — trailing comma after last property. Remove the comma before `}` to validate.
Minify for HTTP body
A 4 KB pretty config shrinks ~30% minified — useful when size matters, though gzip often makes both small on the wire.
When to use this tool
• When an API returns a one-line JSON blob and you need to read nested fields.
• When a CI config or package.json fails parse and you isolate the bad line.
• When you sanitize a payload before sharing in a bug report (redact secrets first).
Debugging APIs with formatted JSON
When a fetch returns 200 but wrong data, pretty-print exposes nesting: is `user.id` missing or renamed? Compare formatted before/after responses in git diff. For GraphQL, errors array often sits beside `data` — indentation reveals partial success. Redact Authorization headers and tokens before pasting into any tool, even local ones, on shared recordings.
Frequently asked questions
What makes JSON invalid?
Unquoted keys, single quotes, trailing commas, comments (non-standard), NaN/Infinity literals, or mismatched brackets.
Does it preserve key order?
Yes — parsed objects re-serialize in insertion order for keys as parsed (ES2015+ behavior).
Can I format JSON with secrets?
Processing is local — safer than cloud formatters — but still avoid pasting production keys on shared screens.
Pretty-print vs minify?
Pretty for humans; minify for storage or embedded scripts. Semantically identical if valid.
Does it fix JSON automatically?
It reports errors; some issues (trailing commas) you fix manually. It does not guess at corrupted data.