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NDJSON/JSONL Viewer

Parse and view JSONL (newline-delimited JSON) with interactive table, filtering, sorting, and export

NDJSON/JSONL Viewer

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5 of 5 lines valid

Total lines: 5Valid: 5Unique keys: 11
#
infoSession started2026-02-12T10:00:00Zusr_123login
debugAPI request2026-02-12T10:01:15Zusr_123/api/v1/dataGET
warnRate limit approaching2026-02-12T10:02:30Zusr_1235
errorDatabase connection timeout2026-02-12T10:03:45Zusr_456ETIMEDOUT3
infoSession ended2026-02-12T10:05:00Zusr_123300000

What this tool does

You can view and validate a JSONL or NDJSON file in the browser without uploading it. The NDJSON/JSONL Viewer parses each line as a separate JSON object entirely on your device, reports invalid lines with line numbers, and renders valid records in a sortable, filterable table. No file ever leaves your machine — there is no server upload.

Updated . Provided as is. Check the output before you rely on it in production.

How to use NDJSON/JSONL Viewer

  1. 1

    Load JSONL or NDJSON

    Paste JSONL (one JSON object per line) or load a .jsonl, .ndjson or .json file.

  2. 2

    Browse the table

    Each line becomes a row and columns are detected from the keys. The summary shows valid lines, parse errors and unique keys.

  3. 3

    Search

    Type in the search box to filter rows by any value across all keys.

  4. 4

    Sort and download

    Click column headers to sort, then download the filtered rows.

Questions and answers

What is NDJSON/JSONL Viewer?
JSON Lines (JSONL, also called NDJSON) stores one JSON object per line, common for logs, event streams and dataset exports. This viewer parses each line, builds table columns from all keys, lets you search, filter by column, sort and expand rows, reports invalid lines, and copies rows as JSON or CSV.
Does NDJSON/JSONL Viewer store or send my data?
No. All processing happens entirely in your browser. Your log data never leaves your device — nothing is sent to any server.
What is the difference between JSONL and NDJSON?
JSONL (JSON Lines) and NDJSON (Newline Delimited JSON) are the same format — one JSON object per line, separated by newlines. Both are commonly used for log files, data streaming, and bulk data processing.
For AI agents: how to call this tool

Machine-readable contract, endpoints and examples. Humans can ignore this section.

Best Path For Builders

Browser workflow

Runs instantly in the browser with private local processing and copy/export-ready output.

Browser Workflow

This tool is optimized for instant in-browser execution with local data handling. Run it here and copy/export the output directly.

/jsonl-viewer/

For automation planning, fetch the canonical contract at /api/tool/jsonl-viewer.json.

How do I view and validate a large JSONL file in the browser without uploading it?

Open the viewer, then paste your JSONL content or load a local .jsonl, .ndjson, or .json file. The file is read with the browser's FileReader API and parsed line by line in the page itself, so nothing is transmitted to a server. Because there is no upload step, the practical size limit is your browser's memory, not a network quota.

Step by step

  1. Paste JSONL text into the input, or use the file picker to open a local file — it is read locally, never uploaded.
  2. Each line is parsed as an independent JSON object. Invalid lines are listed with their line number and parse error, so you can fix the exact offending records.
  3. Lines that parse but are not JSON objects (bare arrays or primitives) are flagged separately, since JSONL tooling expects one object per line.
  4. Browse valid records in the table: sort by any column, filter per column, or search across all fields.
  5. Export the filtered result when you are done.

What makes a JSONL file valid?

Rule Detail
One JSON value per line Every line must be a complete, self-contained JSON document. In practice each line is an object.
Newline separated Records are separated by newline characters. There is no enclosing array and no commas between records.
No trailing commas or comments Each line must be strict JSON. Trailing commas, single quotes, and comments fail per-line validation.
Blank lines are skipped Empty lines are ignored by the parser rather than reported as errors.

Is JSONL the same as NDJSON?

Yes. JSONL (JSON Lines) and NDJSON (Newline Delimited JSON) describe the same format: one JSON object per line. It is the standard shape for log files, event streams, LLM fine-tuning datasets, and bulk exports, because each record can be read, validated, and streamed independently.

Why does no-upload matter for log data?

JSONL files are usually production logs, event exports, or training data — content that often contains user identifiers, prompts, or internal system details. A client-side viewer removes the data-handling question entirely: the parsing code runs in your browser tab, and closing the tab discards everything.