JSONL Validator
Validate JSONL and fine-tuning datasets line by line.
JSONL input
One JSON object per line
Drop a file here
Drop a .jsonl or .ndjson file
Validates every record against your schema
Validation
Line 2
- At least 2 messages are required
- No assistant message to learn from
{"messages":[{"role":"user","content":"Bye"}]}
About the JSONL Validator
Check every line of a JSONL / NDJSON file for valid JSON, then apply dataset rules such as the OpenAI chat fine-tuning shape or prompt/completion pairs, and optionally validate each record against your own JSON Schema. Download only the valid lines.
Examples
Chat dataset
{"messages":[{"role":"user","content":"Hi"}]}Output
Line 1: No assistant message to learn fromKeyboard shortcuts
- Copy the main outputCtrl / ⌘ + Shift + C
- Download the resultCtrl / ⌘ + S
- Share this toolCtrl / ⌘ + Shift + S
- Reset the inputsAlt + R
- Open the tool search paletteCtrl / ⌘ + K
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Frequently asked questions
Version 1.0.0 · Updated 2026-08-14 · Runs entirely in your browser