This tool indents JSON so it can be read, validates it so you can find the mistake, and warns about a failure mode almost every other viewer hides: JavaScript cannot represent integers beyond about nine quadrillion, so a large database id is silently rounded on the way in and displayed as a different number entirely.
Runs entirely in your browser — nothing you paste is uploaded.
How to
Type, paste, or load a .json file. Validation runs as you type, so an error appears the moment it exists.
A failure reports the line and column and shows the line itself, rather than a bare message about an unexpected token.
Choose an indent for reading, or minify to the smallest valid form for transport. Keys can be sorted recursively to make two documents comparable.
If the document contains integers beyond JavaScript's exact range, they are listed — a real problem when those values are database identifiers.
Examples
Parsed as a JavaScript number, this becomes ...992. Every viewer built on JSON.parse displays the wrong value silently; here it is flagged before you copy it somewhere that matters.
JSON forbids trailing commas even though JavaScript allows them. The location makes it findable in a document of a few thousand lines.
Sorting recursively puts two documents into the same shape, so a diff shows genuine differences rather than every reordered key.
Why use it
A line, a column and the text of the offending line, instead of a message that tells you only that something is wrong somewhere.
Large integers are detected in the raw text before parsing, which is the only point at which the information still exists.
Recursive key sorting turns two structurally identical payloads into two identical files, which is what makes a diff useful.
API responses pasted into a viewer routinely contain tokens and personal data. None of it leaves your browser.
Good to know
Summary
FAQ
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