What kinds of JSON errors can this fix?

Single quotes, unquoted keys, trailing commas, // and /* */ comments, smart quotes, NaN/undefined/Infinity, and missing closing brackets.

Will it always produce valid JSON?

Most common issues are fixed automatically, but severely malformed input may still fail — the error message will explain why.

Does it show what was changed?

Yes, a list of applied fixes appears below the repaired output.

JSON Repair / Auto-fixer

Auto-fix broken JSON: quotes, trailing commas, comments, and more.

Works Offline

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Broken JSON

Repaired JSON

{
  "name": "Ada Lovelace",
  "active": true,
  "tags": [
    "math",
    "logic"
  ],
  "score": null,
  "bio": null,
  "address": {
    "city": "London",
    "zip": "90210"
  }
}

Fixes applied

Removed // line comments
Converted single-quoted strings to double-quoted
Added quotes around unquoted object keys
Replaced NaN/undefined/Infinity with null
Removed trailing commas
Added missing closing brackets/braces

About the JSON Repair / Auto-fixer

Repair malformed JSON produced by hand-editing or logging by tolerantly fixing single quotes, unquoted keys, trailing commas, comments, smart quotes, NaN/undefined, and missing brackets. See exactly which fixes were applied.

Examples

Trailing comma & single quotes

{'a': 1, 'b': 2,}

Output

{
  "a": 1,
  "b": 2
}

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Frequently asked questions

Version 1.0.0 · Updated 2026-08-10 · Runs entirely in your browser