Free AI data tool · Formats
JSONL viewer and explorer
Quick answer
A JSONL file is hard to read in a text editor: one long JSON object per line, no formatting, no way to jump around. This JSONL viewer opens the file in your browser and shows it as records you can page through, expand and search. Paste the text or choose a .jsonl or .ndjson file, press Load records, and you get one card per record, a summary of every field and its types, and a search box that filters what you loaded. Nothing is uploaded — the file is read by your browser and never leaves your device.
Your sample is processed in this browser. File contents are not uploaded.
Supported input
.jsonl / .ndjson text, up to 10 MiB or 25,000 records.
How it works
Each line is parsed as JSON; invalid lines are counted and listed by number but not shown as records. Field summaries count how many object records contain each top-level key and which JSON types appear. Search is a literal, case-insensitive substring match on each record's JSON text — no regular expressions or fuzzy matching.
Limitations
- Search covers only the records that were loaded. If the file was cut off at the record limit, matches beyond it are not found.
- The tool does not fetch files from URLs; paste or upload them instead.
Questions
- How do I open a JSONL file?
- Paste or upload it here and press Load records. You can page through records, expand any one, and search. On your own computer, any text editor opens JSONL, but long files are hard to read that way.
- What is a JSONL file?
- JSON Lines is a text format with one JSON object per line. It is the standard format for AI training data and fine-tuning datasets because it can be read one record at a time. See the 'What is JSONL?' explainer linked below.
- Can it open large JSONL files?
- Up to 10 MiB or 25,000 records per file in this browser tool. For larger files, check a sample here first.
- Is my file uploaded anywhere?
- No. The file is parsed by your own browser. Its contents are never sent to a server, which makes the viewer safe for confidential datasets.
- Is my file uploaded?
- No. The file is read and processed in this browser tab, and its contents are not sent to SourceX or anyone else. Closing the tab or pressing Reset clears it.
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