JSON repair automatically fixes common syntax errors that make JSON invalid. It converts single quotes to double quotes, adds missing quotes around keys, removes trailing commas, removes comments, and replaces NaN/undefined with null.

Why does my JSON have errors?

Common causes: writing JavaScript object syntax instead of JSON (single quotes, unquoted keys), copying from code with comments, trailing commas from array edits, or using values like NaN and undefined that JSON doesn't support.

What errors can be automatically fixed?

This tool fixes: single quotes → double quotes, unquoted keys → quoted keys, trailing commas → removed, // and /* */ comments → removed, NaN/Infinity → null, undefined → null.

What if my JSON still has errors after repair?

Complex structural errors like mismatched brackets, incorrect nesting, or invalid escape sequences may require manual fixing. The tool shows remaining error details to help you fix them.

JSON Repair - Fix JSON Syntax Errors Automatically

Input JSON (with errors)Paste your broken JSON

Repaired JSON

Repaired JSON will appear here...

Common JSON Errors This Tool Fixes:

Single quotes → Double quotes

Unquoted keys → Quoted keys

Trailing commas → Removed

Comments → Removed

NaN/Infinity → null

undefined → null

LLM/AI Output Fixes:

Markdown wrappers → Strip ```json ... ```

Truncated JSON → Auto-close brackets

Python True/False → true/false

Python None → null

Unquoted values → Quoted strings

Hex numbers → Decimal (0x1A → 26)

Whitespace in values → Trimmed

Multiple objects → Wrapped in array

What is JSON Repair?

JSON Repair automatically fixes common syntax errors in JSON data, including errors specific to LLM/AI output. Many developers accidentally write invalid JSON - using single quotes, forgetting quotes around keys, leaving trailing commas, or adding comments. AI tools like ChatGPT and Claude can also produce malformed JSON with markdown wrappers, Python-style booleans, truncated output, and more. This tool detects and fixes all these issues, transforming invalid JSON into valid, parseable data.

How to Use

Paste your invalid or broken JSON into the input field.
Click 'Repair JSON' to automatically fix common errors.
Review the repair actions list to see what was fixed.
Check the repaired output - if still invalid, manual editing may be needed.
Copy the repaired JSON and use it in your application.
Use 'Load Sample' to see examples of common errors and how they're fixed.
Use 'Load LLM Sample' to see AI-specific errors like markdown wrappers, Python booleans, and truncated output.

Why Use This Tool?

Fix JSON from APIs that return slightly malformed data

Repair JSON configuration files with syntax errors

Convert JavaScript-like object syntax to valid JSON

Fix LLM/AI output: strip markdown wrappers, convert Python booleans, repair truncated responses

Quickly fix copy-pasted JSON with formatting issues

Understand what went wrong with detailed repair actions

Save time debugging JSON syntax errors manually

Tips & Best Practices

Load Sample to see common error patterns and how they're fixed
Load LLM Sample to see AI-specific errors like ```json wrappers and Python-style values
If repair can't fix all errors, the remaining error message helps identify what's wrong
Use JSON Validator after repair to double-check the result
Complex structural errors may require manual fixing
Comments are removed because JSON doesn't support them
When truncated JSON is detected, a warning will appear - the data may be incomplete

Frequently Asked Questions

What types of errors can this tool fix?

This tool fixes: single quotes → double quotes, unquoted keys → quoted keys, trailing commas → removed, JavaScript comments → removed, NaN/Infinity → null, undefined → null. It also fixes LLM/AI-specific issues: markdown code wrappers (```json), Python-style booleans (True/False), Python None, unquoted string values, hexadecimal numbers, whitespace in values, multiple JSON objects, and truncated output.

How does it fix LLM/AI output?

LLMs like ChatGPT and Claude often produce JSON with specific issues: wrapping output in ```json code blocks, using Python-style True/False/None instead of true/false/null, leaving string values unquoted, outputting hexadecimal numbers, and truncating responses mid-JSON. This tool detects and fixes all these patterns automatically.

Why are single quotes invalid in JSON?

JSON specification requires all strings (both keys and values) to use double quotes. Single quotes are JavaScript syntax but not valid JSON. This tool converts 'text' to "text" automatically.

What happens with truncated JSON?

When LLM output is cut off mid-response, the tool counts open brackets and braces, then adds the missing closing characters. A warning appears to let you know the JSON was truncated - while the result is parseable, some data may be incomplete.

What if the JSON can't be fully repaired?

Some errors require manual fixing, like mismatched brackets, incorrect nesting, or complex structural issues. When automatic repair can't fully fix the JSON, the tool shows what it fixed and the remaining error message to help you fix manually.

Can I repair large JSON files?

Yes, the tool handles JSON files of any size that fit in your browser's memory. For very large files (many MB), the repair process may take a few seconds but works the same way.

Is my JSON data secure?

Absolutely. All repair operations happen in your browser using JavaScript. Your data is never sent to any server, never stored, and never logged. Close the page and all data is cleared.

Should I use this for production data?

This tool is great for debugging and fixing JSON quickly. For production systems, always validate your JSON generation code to prevent these errors at the source. Use JSON Validator to double-check repaired data before using it.

JSON Repair