JSON Repair Tool
Paste malformed JSON and instantly repair trailing commas, single quotes, comments, unquoted keys, and Python literals — with a line-by-line change preview,
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What is JSON Repair Tool?
JSON Repair Tool is a free online utility that fixes malformed JSON so it parses cleanly again. It runs a context-aware parser over your input and repairs the most common mistakes: trailing commas, single-quoted strings, JavaScript-style comments, unquoted keys, Python literals like True and None, NaN and Infinity values, hex numbers, missing commas, and config-style equals signs. Every fix is reported with its line and column, and the whole process happens locally in your browser — nothing is uploaded.
Key Benefits
- Turn unparseable JSON from logs, LLM output, or API responses into valid JSON in seconds
- Structure-aware repairs instead of blind find-and-replace that can corrupt string contents
- Transparent change log: line, column, and snippet for every applied fix
- Understands Python dicts, JS objects, and config files — the usual sources of broken JSON
- Private by design: static page, no server round-trip, works offline
Common Use Cases
- •Fixing API responses or log lines that were truncated or hand-edited
- •Converting Python dictionary output into strict JSON
- •Cleaning JSON produced by an LLM that added comments or trailing commas
- •Salvaging config files written in relaxed JSON for editing before strict import
- •Debugging parser errors by comparing the original and repaired versions side by side
How to Use the JSON Repair Tool
- Paste your broken JSON: Copy the malformed JSON — from logs, config files, LLM output, or an API response — into the text box. Repair starts instantly as you type or paste.
- Check the repair status: A green banner confirms the JSON was repaired and now parses cleanly; a red banner shows the remaining parser error if the input is beyond repair.
- Review the change preview: Every applied fix is listed with its line number, column, and a short source snippet, so you can verify each change before trusting the output.
- Copy or download: Use the Copy button for the repaired JSON, toggle Minify for a compact version, or download it as a file. Use Repaired Output to feed the result back in for a second pass.
Key Features
- 12 repair classes: trailing commas, single quotes, comments, unquoted keys, Python literals, NaN, hex numbers, and more
- Context-aware state-machine parser — understands structure instead of naive find-and-replace
- Change preview with line, column, and source snippet for every fix applied
- Minify toggle, one-click copy, and download as a repaired JSON file
- Handles Python dicts, JavaScript-style comments, and config-style equals signs
- Runs entirely in your browser — payloads never leave your machine
Frequently Asked Questions
Does my JSON get uploaded anywhere?
No. The repair parser is plain JavaScript that runs locally in your browser. Nothing is sent to a server, so it is safe to paste logs, tokens, or internal config payloads.
Which malformations can it fix?
Trailing commas, single-quoted strings, unquoted keys, JavaScript-style comments, Python literals (True, False, None), NaN and Infinity, hex numbers, missing commas between members, equals signs used instead of colons, smart quotes, unterminated strings, and stray trailing semicolons.
Why does it convert NaN and Infinity to null?
Strict JSON has no representation for NaN or Infinity — parsers reject them. null is the conventional JSON stand-in, matching how most serializers handle these values.
What happens to bare words that are not valid JSON values?
A bare word used as a value, such as an enum-like string without quotes, gets wrapped in double quotes so the document parses. The change preview flags every occurrence so you can review the result.
Can it repair any broken JSON?
No tool can guarantee that. It targets the most common copy-paste and cross-language mistakes. If the structure itself is ambiguous or truncated, the tool shows the exact remaining parser error instead of guessing.