JSONL to JSON

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.

Specifications

In 3 steps

1. Drop or pick your JSONL file.
2. The tool gathers the lines into one array.
3. Download the JSON file.

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. Since each line is already valid JSON, nesting and data types (numbers, booleans, nested objects/arrays) survive unchanged - this step only gathers lines, it does not reinterpret them. If a line is not valid JSON, the conversion stops citing the line number instead of producing silently wrong output.

FAQ

Related tools

JSON to JSONL · CSV to JSON · JSON to CSV · XML to YAML · YAML to XML · JSON to Markdown