NDJSON Viewer
Open NDJSON / JSON Lines files in your browser — logs, LLM training data, MongoDB exports. Records are line-paginated, lazy-expanded, and searchable across the whole file.
What is NDJSON?
Newline-delimited JSON (also called JSON Lines or .jsonl) stores one complete JSON value per line instead of one big array or object. It's the standard export format for application logs, streaming data pipelines, MongoDB dumps, and LLM fine-tuning datasets, because each line can be read, appended, or processed independently without parsing the whole file.
{"ts":"2026-07-01T09:00:00Z","level":"info","msg":"server started"}
{"ts":"2026-07-01T09:00:02Z","level":"error","msg":"db timeout","retry":1}
{"ts":"2026-07-01T09:00:05Z","level":"info","msg":"db reconnected"}What you can do with it
- • Auto-detects NDJSON vs. standard JSON on load, so you don't have to pick a mode manually
- • Line-paginated rendering keeps files into the hundreds of megabytes responsive
- • Expand any individual record into the same tree view used by the JSON viewer, with type badges and click-to-copy JSONPath
- • Search keys or values across every line, not just the ones currently on screen
- • We never see your data — parsing happens locally, line by line, in your browser
Not line-delimited?
If your file is a single JSON document rather than one object per line, use the plain JSON Viewer (or the Large JSON Viewer for very large single documents) instead. If some of the lines in your NDJSON file are malformed, run them through JSON Repair first.
FAQ
What's the difference between NDJSON and JSON Lines?
They're the same format under different names — one JSON value per line, newline-separated. Files are typically saved with a .ndjson or .jsonl extension.
Can it handle huge log files?
Yes — pagination is by line, so the viewer only renders the records currently in view rather than the entire file at once.
Is my log data uploaded anywhere?
No. We never see your data — everything is parsed and rendered locally in your browser.