JSONL Lens
Inspect JSON Lines as readable cards without losing your place in the source file.
Open a .jsonl document, preview every record, and move between raw data and formatted JSON in sync.
JSONL Lens opens a live preview beside your editor. Every physical source line maps to exactly one card—including invalid JSON and empty lines—so the raw document and structured view always stay aligned.
Highlights
- Readable side-by-side preview — formats each JSON value with syntax highlighting.
- Reliable line mapping — keeps valid, invalid, and empty lines visible as independent cards.
- Synchronized navigation — follows the source cursor and jumps back to a line when you select its card.
- Safe copy and refresh — lets you copy formatted JSON and preserves your position while the document changes.
- Lossless inspection — keeps large numeric values exactly as written instead of converting them through JavaScript numbers.
- Native VS Code experience — follows the active theme and provides accessible mouse and keyboard interaction.
Get started
- Open a file ending in
.jsonl.
- Select the preview icon in the editor title toolbar, or run JSONL Lens: Open JSONL Lens from the Command Palette.
- Move the source cursor to reveal the matching card in the preview.
- Select a card—or focus it and press Enter or Space—to return to that source line.
Development
pnpm install
pnpm check
pnpm build
pnpm package
The final command creates jsonl-lens.vsix. Install it locally with:
code --install-extension jsonl-lens.vsix
Development requires Node.js 20.19 or newer and pnpm 10.33.0. The bundled extension remains compatible with the Node.js runtime shipped by VS Code 1.85.
Versioning
The project uses Changesets and semantic versioning:
pnpm changeset
pnpm version:check
pnpm version-packages
pnpm package
Create a changeset with each user-visible change. pnpm version-packages updates the package version and changelog before release packaging.
pnpm version:check verifies that package.json contains a semantic version, pins pnpm, and has a matching CHANGELOG.md section. Changesets' Git-aware status command becomes available after the repository has an initial commit.
Limitations
- Only
.jsonl documents are supported.
- The preview is read-only.
- Extremely large files are not virtualized in this release.
