What kinds of errors does it fix?

It handles the common LLM failure modes — markdown code fences, leading or trailing prose, single quotes, unquoted keys, trailing commas, smart or curly quotes, and JSON truncated mid-object or mid-array. After repairing it validates with a real parser.

How does it handle truncated output?

When a model gets cut off, the JSON often ends mid-value with unbalanced brackets. The tool tracks open braces, brackets, and strings and appends the closing characters needed to make it parseable, so you recover the partial data instead of nothing.

Could a repair change my data's meaning?

The repairs are syntactic, not semantic — quotes, commas, and brackets — so values are preserved. Truncation recovery is the one case to review, since closing an interrupted structure can drop an incomplete final value. The tool flags when it had to close brackets.

Is anything sent to a server?

No. All parsing and repair happens locally in your browser. Your data never leaves the page.

LLM JSON Repair — Gera Tools

LLM JSON repair

Language models are asked to return JSON constantly, and they constantly return JSON that almost parses — wrapped in a markdown fence, sprinkled with trailing commas, using single quotes, or cut off mid-object when the response hit a token limit. This tool applies the standard sequence of safe repairs and then validates the result with a real parser, so you get usable JSON instead of a stack trace.

How it works

The repair runs as an ordered pipeline. First it strips markdown fences and any prose before the first { or [ and after the last matching bracket. Then it normalizes smart quotes to straight quotes, converts single-quoted strings and keys, quotes bare keys, and removes trailing commas before closing brackets. Finally it scans for unbalanced braces, brackets, and an unterminated string — the signature of a truncated response — and appends the closing characters needed to make it parse. Every result is run through JSON.parse to confirm validity before it is shown.

Notes and limits

Repairs are syntactic. Quotes, commas, and brackets get fixed; your values are not interpreted or altered.
Truncation recovery is best-effort. Closing an interrupted structure can drop a half-written final value — the tool tells you when it closed brackets so you can spot-check.
Review when warned. If the tool reports it normalized quotes or balanced brackets, glance at the output around the end of the data.
Everything is local. Nothing is uploaded; paste sensitive payloads freely.