Line-by-line validation
Find invalid JSON rows and identify where the dataset needs cleanup.
Free. Private. No uploads.
JSONL Validator
Validate JSON Lines data for AI, ML and developer workflows directly in your browser. Pocket Dev checks line-by-line JSON and common dataset shapes without uploading files.
What it does
Validate JSONL before using it in data or AI workflows.
JSONL Validator helps developers check each line of a JSON Lines file or pasted dataset. Use it for AI training examples, chat message arrays, prompt completion rows, logs and structured local data.
Expected shape checks
Check for any object, prompt-completion rows or messages array rows.
No dataset upload
The JSONL text stays in your browser while it is validated.
How to use
Use JSONL Validator in a few steps.
- Open the JSONL Validator tool inside Pocket Dev.
- Paste JSON Lines data into the input area.
- Choose an expected shape if needed.
- Review validation results and fix any failing rows.
FAQ
JSONL Validator questions
Is this JSONL validator free?
Yes. Pocket Tools is free to use.
Can it validate chat message datasets?
Yes. It can check rows with a messages array shape.
Are datasets uploaded?
No. JSONL validation happens locally in your browser.