NDJSON Viewer
Open NDJSON and JSON Lines files in your browser — logs, LLM training data, MongoDB exports. Read them a page at a time, open any single line, and search the whole file.
Looking for a JSONL viewer, or a JSON Lines viewer? Same thing — .ndjson and .jsonl are one format under three names, and this opens all of them.
What is NDJSON?
Newline-delimited JSON (also called JSON Lines, or .jsonl) puts one complete JSON value on each line, instead of wrapping everything in one big list. That way a program can read, add, or process a single line without touching the rest of the file. It is the usual format for application logs, streaming data, MongoDB dumps, and LLM training sets.
{"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
- • It works out which format your file is in, so there is no mode to choose
- • It shows a page of lines at a time, so even a file of hundreds of megabytes stays quick
- • Open any single line into the same tree the JSON viewer uses
- • Search every line in the file, not just the ones on screen
- • We never see your data — it is all read in your browser, line by line
Not line-delimited?
If your file is one JSON document rather than one object per line, use the JSON Viewer — or the Large JSON Viewer if it is very big. If some lines are broken, run them through JSON Repair first.
FAQ
What's the difference between NDJSON and JSON Lines?
None — they are two names for the same thing: one JSON value per line. Files usually end in .ndjson or .jsonl.
Can it handle huge log files?
Yes — it shows one page of lines at a time, so it never has to draw the whole file at once.
Is my log data uploaded anywhere?
No. We never see your data — it is all read and shown inside your own browser.