JSON Repair.

Repair JSON online - fix broken JSON privately

A JSON repair tool turns almost-valid text into valid JSON. Paste broken JSON above to fix trailing commas, single quotes, unquoted keys, comments, Python values, smart quotes, and broken AI-generated JSON. The tool validates the output and keeps the whole process client-side.

How to repair JSON in three steps

1. Paste the broken JSON — code fences, prose, and all.
2. Press Repair JSON to fix quotes, commas, comments, and braces.
3. Review the repair log before you trust the output.

Built for invalid JSON and LLM JSON

Many AI tools return JSON inside Markdown fences or with small syntax mistakes. This fix JSON workflow removes those wrappers, repairs common syntax issues, and shows what changed so you can review the result before using it in an app, API call, or config file.

Language models generate text one token at a time, so nothing forces the output to be syntactically valid — and the damage is remarkably consistent. This is what a typical broken LLM response looks like:

Sure! Here's the JSON you asked for:

```json
{
  // the user record
  'name': 'Ada',
  "active": True,
  "score": 42,
  "tags": ["admin", "dev",],
```

Six separate problems, all at once:

• Prose before the JSON (“Sure! Here's…”)
• A Markdown ```json code fence wrapping it
• A // comment, which JSON does not allow
• Single quotes instead of double quotes
• Python's True instead of true
• A trailing comma, and the closing brace missing entirely (truncated)

Repaired:

{
  "name": "Ada",
  "active": true,
  "score": 42,
  "tags": ["admin", "dev"]
}

The JSON errors this fixes — and what they mean

Expecting property name enclosed in double quotes — unquoted keys or single quotes. Your text is a Python dict or a JavaScript object literal, not JSON.

Unexpected token } in JSON at position … — a trailing comma before the closing brace or bracket. Legal in JavaScript, illegal in JSON.

Unexpected end of JSON input — the input is truncated, with braces left unclosed. Usually an LLM hitting its token limit, or a partial download.

Unexpected token N in JSON — a Python None, True, or NaN. JSON only knows null, true, false.

One honest warning about auto-repair

Repairs are syntactic. They fix quotes, commas, and braces — they never invent values. That matters most for truncated input: if an LLM was cut off after 8 of 50 records, closing the brackets produces perfectly valid JSON containing 8 records. The other 42 are genuinely gone, and no tool can recover them.

This is exactly why the repair log exists, and why this tool shows one instead of silently rewriting your data. Read it before you push the output into a pipeline — “valid” and “complete” are not the same thing.

Why use this JSON fixer?

It is private, fast, and transparent. After repairing, you can format the JSON, validate the JSON, or compare it with the original. For a deeper walkthrough, read how to repair JSON.