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JSON Lines (NDJSON) Viewer

JSON Lines / NDJSON is one JSON object per line, used by streaming logs, ML datasets, and tail-friendly pipelines. This viewer parses every line independently — so a single malformed line doesn't poison the whole file — and surfaces both the parsed table and the bad lines with their JSON error message. A `field:value` filter narrows by content (top-level key or `nested.path` are both supported), and a column picker keeps only the fields you care about for the re-export. Everything runs in the browser; nothing is uploaded.

How to use

  1. Paste lines or drop a `.jsonl` / `.ndjson` file. The table shows automatically.
  2. Filter with `field:value` (substring match) or plain text (matches anywhere in the JSON).
  3. Pick columns in the second box to keep — leave blank to show all keys discovered.

Frequently asked questions

What happens to malformed lines?
They're listed at the bottom with their line number and the JSON parse error. Valid lines on either side of a bad one are still parsed and displayed normally.
Can I filter on nested fields?
Yes — use dotted paths like `user.email:alice` or `events.0.type:login`. The path walks both objects and arrays.
Why do logs and datasets use JSON Lines instead of a JSON array?
Because a file of one object per line can be appended to, split and read with ordinary line tools without parsing the whole document. It also fails gracefully: a crash in the middle of a write damages the last line only, while a truncated JSON array is unreadable from the first byte. That is exactly what you want from a log or a training set that grows all day.
The table shows columns that most of my records do not have. Is that right?
Yes. Records in a JSON Lines file are independent of each other, so the table is the union of every key seen and a record without a key shows an empty cell. That shape is normal for event logs whose fields changed over time — and it means filtering or sorting on a field only reaches the records that actually carry it.

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