How to use
- Paste JSONL or open a
.jsonlfile — it never leaves your browser. - Every line is parsed. Errors and warnings are listed with their line numbers.
- If the data uses the
{"messages": [...]}chat format, it is also checked for valid roles, missing assistant replies and empty messages. - Use the converter to turn a JSON array into JSONL or back.
FAQ
What is JSONL?
JSON Lines puts one JSON object on each line. It is the standard format for LLM fine-tuning datasets, batch API requests and log files because it can be streamed and appended line by line.
Does it check token limits?
Use the Token Counter tool for that. This validator focuses on structure: each line must parse, and chat examples must contain a valid sequence of roles ending in an assistant reply.