JSONL Viewer

Preview a formatted, syntax-highlighted view of any row in a .jsonl / .ndjson file — without copying it into a separate file.

Usage

1. Open a .jsonl or .ndjson file.
2. Place the cursor on the row you want to inspect.
3. Run JSONL: Preview Row via:
   • the keybinding Cmd+Alt+J (macOS) / Ctrl+Alt+J (Windows/Linux),
   • the {} icon in the editor title bar,
   • the editor right-click context menu, or
   • the Command Palette.

A read-only, pretty-printed view of the row opens beside the editor, with full JSON highlighting and folding. While the preview is open, it follows your cursor: moving to another row updates the preview automatically.

Rows that fail to parse show the parse error and the raw line so you can spot the problem.

Large files (over 50 MB)

VS Code does not share files larger than 50 MB with extensions, so the preview cannot follow your cursor in them. The extension still works: it streams rows directly from disk. Use the explicit navigation commands instead:

Extension Settings

• jsonlViewer.followCursor (default true): automatically update the preview as the cursor moves between rows while the preview is open (files under 50 MB only).

Install Locally

Package the extension as a .vsix and install it into VS Code:

npm install
npm install -g @vscode/vsce
vsce package
code --install-extension jsonl-viewer-0.0.1.vsix

Then reload VS Code. To update later, bump the version, re-run vsce package, and install the new .vsix.

Development

• npm run compile — type-check, lint, and bundle.
• npm test — run tests.
• Press F5 to launch an Extension Development Host; open sample.jsonl to try it out.