Fix JSON Errors

The four mistakes that break JSON

The overwhelming majority of parse failures come from a short list of habits carried over from JavaScript or other languages:

• Trailing commas — a comma after the last item, like [1, 2, 3,]. Legal in JavaScript arrays, illegal in JSON.
• Comments — // and /* */ notes that JSON simply does not allow.
• Single quotes — 'value' instead of "value". JSON strings must use double quotes.
• Unquoted keys — {name: "x"} instead of {"name": "x"}. Object keys must be quoted strings.

Enable Repair and the tool fixes all four automatically, then re-formats the cleaned, strictly-valid JSON.

How the repair works

The repairer makes a careful, string-aware pass over your text. It removes line and block comments without touching // sequences that happen to live inside a string value such as a URL. It converts single-quoted strings to double quotes while escaping any embedded quotes correctly. It adds quotes around bare object keys, and it deletes commas that sit just before a closing brace or bracket. Only after those fixes does it hand the result to a strict parser, so what you get back is guaranteed-valid JSON.

When repair can't help

Repair handles syntax conveniences, not genuinely broken structure. If a string is left unterminated, a brace is missing entirely, or two values sit side by side with no separator and no clear intent, there is no safe automatic fix — guessing could silently change your data. In those cases the validator's line-and-column error is your tool: it pinpoints where the structure goes wrong so you can correct it by hand. Repair is for the predictable, mechanical mistakes; the error locator is for everything else.

Safe because it's local

Broken JSON is often something you pasted out of a log, a config or a half-finished API integration — exactly the material that may contain secrets. This repair tool runs in your browser, so none of it is uploaded. You can fix a malformed token payload or a leaked-looking config without sending it anywhere. The repaired, valid JSON appears instantly on the page, ready to copy back into your code.