How it works
The formatter runs JSON.parse on your input, then writes the parsed value back with two-space indentation. Because it parses first, the output is a canonical representation: numbers are normalised, duplicate keys collapse to the last value, and property order follows the document, not the alphabet.
- Formats with JSON.parse + JSON.stringify, so 1.0 becomes 1 and duplicate keys collapse; formatted output is re-serialised, not byte-preserved.
Why it matters
APIs fail on malformed JSON far more often than on bad values, and the error message usually points at the symptom rather than the cause. Seeing the whole document laid out, with the failing line highlighted, turns a frustrating hunt into a one-minute fix.
A worked example
Paste {"b": 2, "a": 1} and format it. The output keeps the order the document was written in, uses two spaces of indentation and shows 2 keys and 16 bytes underneath. Minify the same input and you get {"b":2,"a":1} back.
Common mistakes
- Expecting formatting to sort keys — it preserves document order.
- Pasting JavaScript object literals with comments or single quotes.
- Confusing a validator with a schema check: types are not enforced.
Practical tips
For payloads over a few megabytes, switch to minifying first — it makes the file smaller and easier to scan. If validation keeps failing near a specific line, paste only that fragment; the line numbers will be local to the fragment and easier to reason about.
How to use it
- Open the tool. Everything runs in your browser tab.
- Paste or type your input, then choose the action you need.
- Check the result and copy it with one click.
Common questions
What does the validator catch?
Syntax errors, with the line and column where JSON.parse stopped. It reports the first error only.
Why did 1.0 become 1 after formatting?
JSON does not distinguish 1 from 1.0. Formatting re-serialises the parsed value, so number formatting and duplicate keys collapse.
Can it handle very large JSON?
Files of a few megabytes work in the tab; much larger documents can be slow on phones with limited memory.
Is this tool really free?
Yes. There is no account, no paywall and no usage limit. Tools App is funded by aumenso, the studio behind it.
Is anything I enter uploaded?
No. The tool runs in your browser tab; what you enter is never sent to us and never stored.