Turn JSON Lines or NDJSON into one JSON array, keeping big numbers exact
Runs in your browser. Nothing you type is sent anywhere. Checked against sources on 16 Oct 2026.Many tools want one JSON array, while logs, exports and machine-learning datasets come as JSON Lines, one record per line. Paste or open the JSONL file and get a JSON array with every record written exactly as it was, so long IDs such as 12345678901234567890 are not rounded. Any broken line is listed with its number first, so nothing is dropped without notice.
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JSON Lines, also published as NDJSON, is the format of logs, analytics exports and machine-learning datasets: one JSON value per line, so a program can stream or append records without reading the whole file. An ordinary JSON viewer rejects such a file outright, because the file as a whole is not one JSON document.
| View | What you get |
|---|---|
| Table | The first 200 records, one column per key, nested values as JSON |
| JSON array | All records between brackets, each written exactly as in the file |
| Pretty JSON | The same array, indented |
| JSON Lines | Clean lines: trimmed, empty lines removed |
Converting both ways. Paste a JSON array instead and it is read as its elements, ready to save as JSON Lines for BigQuery, Elasticsearch or a fine-tuning upload. The JSON array view copies each record's own text, so a 20-digit ID is never rounded; when a view would round one, a note says so.
The rest of the article, and all 6 questions about JSONL Viewer and Validator, are on the JSONL Viewer and Validator page.
A JSONL file, also called JSON Lines or NDJSON, holds one complete JSON value on each line, usually one object per record. Logs, database exports and machine-learning datasets use it because a program can read or append one line at a time without loading the whole file.
Open the .jsonl or .ndjson file here, or paste its lines, and every record appears in a table with one column per key. Bad lines are listed with their line number and column. The file is read by your browser itself, so even a confidential export never leaves your device.
Switch the output to JSON array and the records are wrapped in square brackets with a comma after each, written exactly as they appear in the file. Pretty JSON indents them instead. Download saves the result as a .json file ready for any tool that expects one array.
Paste the JSON array, pretty or on one line, and it is read as its elements. Switch the output to JSON Lines and each element is written compactly on its own line, the layout that BigQuery, Elasticsearch bulk loads and fine-tuning uploads ask for.
Rates and rules change; check the source before you rely on a figure.
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Same job, other tools: JSON Minifier – Strip whitespace from JSON for production · JSON Validator – Check JSON and see exactly where it breaks · Content-Type Header – The exact Content-Type header to send, including when to add charset=utf-8.
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