What JSONL format does this tool output?

Each line is a JSON object with a "messages" array containing objects with "role" (system/user/assistant) and "content" fields. This matches OpenAI's fine-tuning format and is compatible with most LLM providers.

What if my data does not have a system column?

You can leave the system column unassigned — the tool will simply omit the system message from those rows. You can also assign the same column to multiple roles if needed.

How large a dataset can I process?

The tool processes data client-side in the browser. It handles thousands of rows comfortably. For very large datasets (100K+ rows), consider splitting the file and processing it in batches.

AI Dataset Formatter

Convert CSV, TSV, or JSON data to JSONL format for LLM fine-tuning with role mapping.

Input data (CSV / TSV / JSON)

Paste data above to begin formatting

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FAQ

What JSONL format does this tool output?: Each line is a JSON object with a "messages" array containing objects with "role" (system/user/assistant) and "content" fields. This matches OpenAI's fine-tuning format and is compatible with most LLM providers.
What if my data does not have a system column?: You can leave the system column unassigned — the tool will simply omit the system message from those rows. You can also assign the same column to multiple roles if needed.
How large a dataset can I process?: The tool processes data client-side in the browser. It handles thousands of rows comfortably. For very large datasets (100K+ rows), consider splitting the file and processing it in batches.

Transform structured data into JSONL fine-tuning format. Paste CSV, TSV, or JSON data and the tool auto-detects the format and columns. Map columns to system, user, and assistant roles, then export as JSONL with standard messages format. Supports downloading the output file.