Convert JSON Lines (NDJSON) to a JSON array locally - one record per line, no upload, right in your browser.
Running locally on your device ...
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Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
JSON Lines, also called NDJSON, stores exactly one JSON value per line. The format is the standard for log files, data exports, streaming processing and machine-learning training data, because a file can be read and appended line by line without loading the whole thing into memory. Many tools, by contrast, expect a single JSON array. This tool reads your .jsonl file and gathers every line into one readable JSON array.
The conversion runs entirely locally in your browser, in pure JavaScript. Every non-empty line is parsed individually as JSON and taken into the array in its original order; blank lines are skipped. The result is indented with two spaces and ready to use right away - for instance to inspect a log excerpt in an editor or to hand an NDJSON export to an interface that only accepts arrays.
If a line is not valid JSON, the tool does not fail silently but names the exact line number and the cause - so you find the error quickly in large files. The reverse direction, a JSON array back into JSON Lines, is handled by our JSON to JSONL tool. Nothing is uploaded; your data stays on your device.
| Input formats | JSONL, NDJSON |
|---|---|
| Output format | JSON |
| Batch processing | No |
| Processing | Locally in your browser (JavaScript) |
| File upload | None |
Limitations: Expects exactly one JSON value per line (JSON Lines / NDJSON). Blank lines are skipped, all remaining lines are joined into an array in their order and emitted indented with two spaces. If a line is not valid JSON, the conversion stops citing the line number instead of producing silently wrong output.
No. The conversion runs entirely locally in the browser - nothing is sent.
NDJSON is another name for JSON Lines: each line holds exactly one JSON value.
You are told the exact line number and the cause - no silent failure.
Yes. The entries appear in the array in the original order of the lines.
Yes, with our "JSON to JSONL" tool.