Free JSONL / NDJSON Viewer

JSONL (JSON Lines) is a format where each line is a valid JSON object, commonly used for log files and data streams.

Yes — if all records share the same keys, export as CSV.

Yes, completely free.

Absolutely. The JSONL / NDJSON Viewer processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the JSONL / NDJSON Viewer is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the JSONL / NDJSON Viewer in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The JSONL / NDJSON Viewer works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

A regular JSON file holds one value — usually a single array or object — that must be read as a whole, so the entire file has to be valid and loaded into memory before anything can be used. JSONL (also called JSON Lines or NDJSON) instead puts one complete, standalone JSON object on each line, separated by line breaks. There are no enclosing brackets and no commas between records, which lets programs append, stream, and process records one line at a time without parsing the whole file. That is why logging systems, OpenAI fine-tuning datasets, and BigQuery exports favor it. This viewer is built around that line-by-line structure: it splits your input on line breaks and reads each line as its own record, then shows them as a table or a collapsible JSON list. Paste a file above to see the records and key counts instantly.

Because JSONL parses each line on its own, a single broken record will not stop the rest of the file from loading, but it can quietly get skipped during an import. This viewer parses every line independently and reports any that fail in a separate "Parse errors" panel, listing each problem with its exact line number and the underlying JavaScript error message — for example a trailing comma, an unquoted key, or a string that was truncated mid-write. That lets you jump straight to the offending row instead of scanning thousands of lines by hand or guessing why a fine-tuning job or database import rejected the batch. Blank lines are ignored, so empty rows never count as errors. Paste your file above, click Parse, and any malformed lines are flagged by number so you can fix them before re-running your pipeline.

The viewer offers two ways to read your data and picks what fits automatically. The table view appears only when your data is "tabular" — meaning every record is a flat JSON object — and lays out one column per key and one row per record, which is ideal for log lines or exports where each entry shares the same simple shape. The header shows the union of every key seen across all records, so a field present in only some rows still gets its own column. The JSON list view works for any data, including arrays and deeply nested objects: it shows a numbered, collapsible tree you click to drill into, with strings, numbers, booleans, and nulls color-coded by type. Use the table for quick scanning and CSV export, and the list when records are nested or irregular. Paste your file to switch between both.

Once your file is parsed, the viewer detects every key across your records and offers a simple filter built from that schema. Pick any key from the dropdown, type a value into the box, and the table and list update to show only records whose value for that key contains your text. The match is a case-insensitive substring search, so typing "error" matches "ERROR" and "server_error" alike, and a badge shows how many of the total records currently match. This is handy for isolating one user ID, a single status code, or one error type inside a long log without opening the file in an editor. The filter also drives the exports, so the JSON Array and CSV downloads reflect only the matching rows. Paste your data above, choose a key, and start narrowing down your records.

To stay fast and responsive on large files, the viewer limits how many records it draws on screen at once: the table renders the first 100 records and the JSON list shows the first 50, with a note telling you how many of the total are displayed. This is purely a rendering cap so your browser does not slow to a crawl building a huge DOM — the full dataset is still parsed and fully counted. Every record drives the record total, the detected key count, the tabular check, the filter results, and the exports, so nothing is lost. If you need to see specific rows beyond the visible window, use the key filter to narrow the data down so the records you care about move into view. To work with the complete set, use the JSON Array or CSV export, which always includes every matching record. Paste your file above to get started.