Why does my JSON say it is invalid when it looks fine?

Usually a trailing comma, single quotes instead of double, an unquoted key, or a comment — all legal in JavaScript, none legal in JSON. The validator points at the exact line and column, so look there first.

Does formatting change my data?

Not the content: it re-parses and re-serialises, so only whitespace changes. Key order is preserved unless you ask for a sort, and numbers round-trip as written.

What does sorting keys help with?

Comparing two versions of the same document. Objects are unordered by definition, so an unsorted diff shows moving keys as changing content; sorted keys make a real diff show only real changes.

Can it handle large files?

It parses in the browser tab, so tens of megabytes work but will pause briefly and use memory proportional to the input. Split anything much larger.

Text & Data Ready to use

JSON Formatter

Pretty-print, minify, validate, key-sort or escape JSON in your browser — and see the exact line, column and snippet where a syntax error begins.

JSON input

Operation

Sort order

Used by the “Sort keys” operation.

This tool runs entirely in your browser. Your input never leaves your device.

About JSON Formatter

Two operations cover most of the use. Formatting re-indents with two spaces so a minified API blob becomes readable; minifying removes every insignificant byte, which is what you want before putting JSON into a query string, a fixture, or a payload you are counting the size of. Both re-parse the input first, so nothing is 'formatted' into something that no longer loads.

Validate answers a slightly different question and answers it in detail: yes or no, the root type, the number of top-level keys or array length, and the size before and after. On the no branch it quotes the parser's position as a line and column number and shows the surrounding text with the failure point marked, which is a great deal faster than reading V8's message and hunting for the character. Sort keys rewrites every object with its keys in ascending or descending order — the trick that makes JSON diffs reviewable and snapshot tests stable.

Escape turns arbitrary text into a valid JSON string literal (useful when generating code); unescape does the reverse; value-to-source renders a parsed value back as plain text. None of it leaves the page.