Big JSONL Viewer
Open huge .jsonl and .ndjson files as a fast, searchable table inside VS Code. Built for files that are too big to scroll and for logs that are still being written.
Why use it
- Multi-gigabyte files open instantly. A byte-offset line index is built once and cached, then only the rows on screen are read from disk. A million-line file scrolls like a short one.
- Follows growing logs. The viewer watches the file, extends its index as new lines land, and keeps following the end while you are near the bottom, the way
tail -f does.
- Edit and save in place. Fix a malformed line and press
Cmd/Ctrl+S. The file is rewritten by streaming, so changing a line's length is safe even on very large files.
- Works where the file already is. Remote-SSH, Dev Containers and WSL included. No copying a 4 GB log to your laptop to read three lines of it.
Features
- Table view with columns sampled from the first rows, rendered with virtual scrolling
- Search by substring on the raw line, or
key:value on the parsed object; filter mode hides rows that don't match
- Malformed lines highlighted in place, with the parser's error message
- Expand any row to see the parsed JSON as a tree and the raw line, and edit it inline
- Drag to resize columns
Usage
Open any .jsonl or .ndjson file and it opens in the viewer. To see the plain text instead, run View: Reopen Editor With… from the Command Palette and pick Text Editor.
To edit a line: expand the row, change the raw JSON, click Apply Edit, then Save (or Cmd/Ctrl+S). Discard drops edits you haven't saved.
Privacy
The file is read from disk and rendered in a sandboxed webview. Nothing is uploaded. Telemetry is off by default and this build contains no telemetry endpoint, so it sends nothing.
No VS Code at hand?
jsonl.co is the same viewer in the browser, plus converters between JSONL, JSON, CSV, Excel and YAML. Files are processed locally in the browser and never uploaded. More about this extension: jsonl.co/vscode.
Feedback
Bug reports and feature requests: feedback@jsonl.co
