Format, validate and fix JSON.
Paste JSON to beautify, minify or check it. Errors show the exact line and column, common mistakes can be fixed in one click, and big numbers keep their precision. Nothing leaves your browser.
Runs in your browserNothing uploaded or storedFree, no sign-up
Your JSON
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Paste or type JSON to validate it.
The most common JSON mistakes
Trailing commas
{"a": 1,} is invalid. The last item must not have a comma after it.
Single quotes
JSON needs double quotes: "name", not 'name'. Keys must be quoted too.
Comments
JSON has no comments. Remove // ... and /* ... */, or turn on “Fix common mistakes”.
Wrong literals
Use lowercase true, false and null. Python's True, None and JavaScript's undefined are not valid.
Questions people ask
How do I validate JSON?
Paste it into the box. The page checks it as you type and tells you whether it is valid. If not, it shows the exact line and column of the first problem and a short explanation, and a button jumps to it.
What does “Fix common mistakes” do?
It accepts input that is valid JavaScript-style data but not strict JSON: comments, trailing commas, single-quoted strings, unquoted keys, Python-style True, False and None, and values like undefined and NaN (which become null). The output is always clean, strict JSON.
Will big numbers lose precision?
No. Many tools parse numbers with JavaScript, which silently rounds integers above 9,007,199,254,740,991. This formatter keeps every number exactly as you wrote it, so IDs like 12345678901234567890 stay intact.
What is the Tree view for?
It shows your data as a collapsible outline, which makes large documents easier to explore. Click any key or value to copy its path, such as $.users[0].name, ready to use in code.
What happens with duplicate keys?
Strict JSON allows them but most programs keep only the last one. The formatter keeps all of them in the output and warns you, so nothing is lost silently.
Is my JSON uploaded?
No. It is parsed and formatted in your browser, so private data such as API responses, tokens and configuration never leaves your device.