JSON Formatter

Most JSON problems are not really formatting problems — they are a single misplaced character somewhere in a few hundred lines. The browser's own error for that is famously unhelpful: "Unexpected token } in JSON at position 412" gives you a character offset in a file you are reading as lines. This formatter turns every parse failure into a line number, a column, the offending line of text, and a caret pointing at the character that broke it.

That matters more than it sounds, because JavaScript engines disagree about what they tell you. Chrome alone throws two different message shapes depending on the error, one carrying a position and one carrying only a quoted excerpt, and Firefox and Safari word theirs differently again. All of them are normalised here so you get the same answer whichever browser you are in.

Pretty-printing supports two, four or tab indentation, and minifying strips every byte of insignificant whitespace — useful when you are pasting a payload into a config field with a size limit. Sorting keys alphabetically makes two versions of the same document comparable in a diff, and it deliberately leaves arrays in their original order, because the order of an array is data rather than presentation.

A byte order mark at the start of a file is stripped before parsing. It is invisible, it is common in files exported from Windows tools, and it otherwise causes a failure at position zero with a message that makes no sense.

Nothing you paste leaves the page. That is the point for this tool in particular: the JSON developers most often need to inspect is a real API response with real tokens, real customer records or real keys in it, and pasting that into a website that round-trips it through a server is a genuine leak.