TTULAKITO
AI

JSON Mode Output Cleaner

Extract clean JSON from messy LLM responses with code fences.

All tools

Raw LLM response

Clean JSON

{
  "name": "Ada",
  "skills": [
    "math",
    "engines"
  ],
  "verified": true
}

Frequently asked questions

Why do LLMs wrap JSON in markdown code fences?
Models are trained on a lot of markdown, so they default to ```json ... ``` fences even when asked for raw JSON. Strict JSON mode or response_format helps but isn't universally supported.
What are common JSON output failures from LLMs?
Trailing commas, single quotes, unescaped newlines inside strings, smart quotes, comments, and prose like "Here is the JSON:" prepended before the object. A cleaner strips these before parsing.
Should I still validate the cleaned JSON against a schema?
Yes. Cleaning fixes syntax, not semantics - the model can still hallucinate fields or wrong types. Run JSON Schema or Zod validation after parsing.