JSON Repair

About this tool

Most "broken" JSON in practice isn't broken in some exotic way — it's one of a handful of very common, very specific mistakes that happen when JSON gets hand-written, copy-pasted from a non-JSON source, or edited by someone used to a different language's syntax. A trailing comma left after the last item in an array. Single quotes instead of double quotes, carried over from JavaScript or Python habits. Object keys left unquoted, again a JavaScript convention that isn't valid in strict JSON. Python's True/False/None pasted in where JSON wants lowercase true/false/null. This tool targets exactly that specific, common set of problems.

The most important design decision here isn't which mistakes to fix — it's how to handle the fixing honestly. A repair tool that silently rewrites your data and hands back something different, with no record of what changed, is asking you to trust it blindly, which is a bad position to be in with data you might not have fully reviewed yourself. This tool never does that: every repair pass shows the original text and the repaired result side by side, plus an explicit list of exactly which category of fix was applied — "Removed trailing commas," "Converted single-quoted strings to double-quoted strings," and so on. Nothing is fixed silently, and nothing is guessed at beyond the documented, narrow set of patterns this tool recognizes.

Each fix is applied conservatively, with a bias toward leaving ambiguous cases alone rather than guessing wrong. The single-quote-to-double-quote conversion, for instance, skips any string that already contains a double quote internally, rather than risk corrupting content by guessing how to escape it — an edge case flagged as unfixed rather than silently mishandled. If the repaired result still doesn't parse as valid JSON after every documented fix has been attempted, the tool says so plainly rather than presenting something broken as if it were fixed.

This is meant for the everyday case of cleaning up JSON-like text — from a config file edited by hand, a value copy-pasted from code, an LLM-generated response that's JSON-shaped but not quite strict JSON — not for arbitrary or deeply malformed input. Always review the repaired output and the list of changes before trusting it with anything that matters. Everything runs locally in your browser; nothing you paste is sent anywhere.