JSONL Viewer
Inspect JSONL/NDJSON files with per-line validation — nothing is uploaded
How to use
- Paste JSONL text or drop a .jsonl / .ndjson file onto the input area.
- Each valid line renders as a formatted record; invalid lines are flagged with line numbers and the parse error.
- Use the search box to filter records containing a string.
About this tool
When an ML pipeline or log shipper rejects a JSONL file, the failure is usually one malformed line in a million. This viewer parses each line independently: valid records render as cards, bad lines surface with their numbers and the underlying JSON.parse error message, so repair takes seconds instead of binary-searching a 2GB file.
Frequently asked questions
How big a file can it handle?
It depends on your machine's memory — everything runs locally. Files up to tens of megabytes are typically fine; the record count summary helps you sanity-check imports.
Are my files uploaded?
No. Unlike tools that upload files to a server for processing, this viewer parses everything with JavaScript in your browser tab. Confidential datasets never leave your device.
Can it fix broken lines?
It pinpoints them: you get the line number and the exact parse error so you can fix the source quickly.