Fix JSON Online – Repair Invalid JSON Automatically

Input

Output

Ready

Ln 1, Col 1

Fix invalid JSON in one click

JSON copied from JavaScript, Python, logs or LLM output is often almost valid. Click Repair (or Try auto-repair on the error card) and the tool rewrites it as valid, formatted JSON. The sample above shows a typical case.

How to use it

Paste the broken JSON into the Input panel.
Click Repair in the toolbar. The input is replaced with valid JSON and a summary of the fixes is shown.
Review the result. Press Ctrl+Z to undo if needed.

What Repair fixes

Trailing commas, missing commas and extra commas
//, /* */ and # comments
Single quotes, backticks and curly “smart” quotes
Unquoted keys and bare text values
Python True, False, None; JavaScript undefined, NaN, Infinity
Unclosed or mismatched brackets, JSONP wrappers, const x = prefixes, and newline-delimited JSON

More JSON tools

All tools are free and run privately in your browser.

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JSON Repair FAQ

Can every broken JSON be repaired?

Most common mistakes can. If the input is too ambiguous, Repair tells you where it got stuck. Always review the repaired result before using it.

Can I fix JSON from an LLM or ChatGPT response?

Yes. Model output often has trailing commas, comments, single quotes or a missing closing bracket, which are exactly what Repair fixes.

Can I undo a repair?

Yes. The repair is applied as a normal edit, so Ctrl+Z (Cmd+Z on Mac) restores your original text.

Is my data uploaded to a server?

No. The JSON Repair runs entirely in your browser using JavaScript. Your data is never uploaded, logged or stored, and the tool keeps working offline after your first visit.