JSON Repair Tool

JSON produced by large language models, copied out of logs, or returned by loose APIs is often almost valid but rejected by strict parsers. This tool re-tokenizes the text and rewrites it into strict, JSON.parse-compatible output while recording every change.

Problems it fixes

• Trailing commas — [1, 2, 3,] and {"a": 1,}
• Missing commas between array items and object entries
• Single & smart quotes — 'value', “value” become "value"
• Unquoted keys — {name: "Ada"} becomes {"name": "Ada"}
• Python / JS literals — True, False, None, NaN, undefined, Infinity become valid JSON
• Comments — // line and /* block */ comments are stripped
• Markdown fences — surrounding ```json fences and prose are removed
• Missing brackets — unbalanced { } and [ ] are closed
• Number quirks — .5, 5., leading +, and leading zeros
• Control characters — raw newlines and tabs inside strings are escaped
• Newline-delimited JSON — multiple top-level values are wrapped in an array

Steps

1. Paste your broken JSON into the input box.
2. The repaired result appears automatically (or click Repair JSON).
3. Review the What Was Fixed list and the line-by-line Diff.
4. Copy or download the clean, valid JSON.

You can embed this util on your own site as a widget. Adding ?embed=1 to the URL loads a compact version with just the tool itself; no header, menu, or documentation. Paste this snippet into your HTML:

Copy snippet Adjust the height to taste.