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.

Is my data uploaded to a server?

No. This tool runs entirely in your browser using standard web APIs, so your input never leaves your device and nothing is logged or stored on our servers.

Does it work offline and on mobile?

Yes. Once the page has loaded it keeps working without a network connection, and the layout is responsive so it stays usable on phones and tablets.

JSON Repair / Auto-fixer

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

Support

Works Offline

Privacy First

No Login

No API

Broken JSON

Repaired JSON

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

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

Keyboard shortcuts

Copy the main outputCtrl / ⌘ + Shift + C
Download the resultCtrl / ⌘ + S
Share this toolCtrl / ⌘ + Shift + S
Reset the inputsAlt + R
Open the tool search paletteCtrl / ⌘ + K

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Frequently asked questions

Comments

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