JSON Formatter & Validator
Paste JSON to check it is valid and read it properly.
Runs entirely in your browser — nothing you paste is sent to our servers.
What this tool does
Validation with position
Invalid JSON reports the parser message, which includes the character offset — usually enough to spot a stray comma.
Configurable indentation
Two spaces, four, or tab. Key order and values are preserved exactly.
Minify
Strip every optional byte for sending over the wire, producing identical data.
Local only
Parsed in your browser, so pasting a real API response does not upload it.
Frequently asked questions
Is my JSON uploaded anywhere?
No. Parsing and formatting happen in your browser with the built-in JSON parser. No request is made, so you can safely paste an API response containing real data.
Why does it say my JSON is invalid when it looks fine?
The most common causes are trailing commas, single quotes instead of double quotes, unquoted keys, and comments - all valid JavaScript but not valid JSON. The error message includes the character position, which is usually enough to find it.
What is the difference between formatting and minifying?
Formatting adds indentation and newlines so a human can read the structure. Minifying strips every optional space, which is what you want before sending JSON over the wire. Both produce exactly the same data.
Does formatting change my data?
No. The value is parsed and re-serialised, so key order is preserved and values are unchanged. Note that JSON has no distinct integer type, so 1.0 comes back as 1.
Is there a size limit?
Only your browser memory. Very large documents (tens of megabytes) may make the page briefly unresponsive while parsing, since the work happens on the main thread.
Monitor it, don't just check it
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