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NDJSON / JSONL Viewer

Parse and inspect NDJSON and JSONL files line by line.

Reviewed by · Last reviewed

How to Use the NDJSON / JSONL Viewer

  1. Paste your NDJSON or JSONL content into the input area. Each line should contain one valid JSON value.
  2. Click Parse to process the input.
  3. Review the results below. Valid lines show their formatted JSON; invalid lines display the parse error for that specific line.
  4. Check the summary line to see how many lines parsed successfully and how many failed.

What This Tool Does

The viewer splits the input on newlines, skips blank lines, and runs JSON.parse on each remaining line independently. Each result includes the source line number, the parsed JSON value (formatted with two-space indentation for readability), or the exact error message when parsing fails. This per-line approach means a single malformed entry does not hide the rest of the file - valid and invalid lines are reported side by side. The display is capped at 1000 entries to prevent the browser tab from freezing on large files.

Frequently Asked Questions

What is NDJSON?

NDJSON (Newline Delimited JSON) is a format where each line is a valid JSON value, separated by newlines. It is widely used for log streams, data pipelines, and bulk API exports because each line can be processed independently without loading the entire document into memory.

What is the difference between NDJSON and JSONL?

NDJSON and JSONL are two names for the same line-delimited JSON format. NDJSON stands for Newline Delimited JSON, while JSONL stands for JSON Lines. Both use the <code>.ndjson</code> or <code>.jsonl</code> file extensions and follow the same structure: one valid JSON value per line.

Is my data sent to a server?

No. This tool runs entirely in your browser tab. Your NDJSON or JSONL content is parsed locally using the browser-native <code>JSON.parse</code> function. No data is ever uploaded or transmitted to any server.

How many lines can I parse at once?

The parser processes all lines in the input, but only the first 1000 results are displayed to keep the page responsive. A notice appears when your file exceeds that limit. For very large files, consider using a command-line tool like <code>jq</code> or <code>fx</code>.

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