JSONL Native Reader

Read JSONL and NDJSON as a complete, formatted JSON array in VS Code’s native read-only editor. Original number literals, duplicate keys and string escapes are preserved. Large files remain searchable; VS Code may disable syntax highlighting and folding for them.

[
  {
    "id": 1,
    "message": "First record"
  },
  {
    "id": 2,
    "message": "Second record"
  }
]

Use familiar JSON punctuation, indentation, syntax highlighting, folding, text selection and search. The original JSONL file stays unchanged; large integers, decimals, exponent notation, key order, duplicate keys and string escapes are preserved exactly.

Usage

After installing the VSIX and reloading the window, click a .jsonl or .ndjson file to open the complete formatted JSON view automatically. You can also use the file context menu or Command Palette to run the read command (jsonlNative.open). Command labels in the extension currently appear in Chinese; the identifiers here refer to the actual registered commands.

To view the original text, use the source command (jsonlNative.source) from the file context menu. Automatic reading remains suspended while that source tab is open. Close it and click the file again to resume automatic reading. Files with unsaved changes and diff views do not switch automatically.

Search for jsonlNative.autoOpen in Settings to disable automatic opening and use the commands manually.

• Use Ctrl+F to search, and select or copy JSON as usual.
• Use the folding arrows or Ctrl+K Ctrl+0 to fold, and Ctrl+K Ctrl+J to unfold.
• Place the cursor in a record and run jsonlNative.source to open the original file beside the reader. For regular files, the cursor moves to the source line for that record.
• When the source changes, the status bar prompts you to refresh. Click the status bar item or the refresh button at the top right of the editor.
• The loading notification supports cancellation.

Opening and refreshing use unsaved source text when it is accessible to the extension. Files beyond VS Code’s extension synchronization size limit are read from disk, so save the source first. The reading view remains a snapshot; file changes do not interrupt reading automatically. If the source structure has changed, refresh before jumping to the source to use the updated line mapping.

File support and size limits

Requires VS Code 1.96 or later. Supports UTF-8, UTF-8 BOM, LF and CRLF. Blank lines are skipped; invalid UTF-8 produces an explicit error. Invalid JSON lines are preserved with diagnostics identifying the physical source line, so the resulting array may also be invalid JSON.

The entire file becomes one native document, without pagination. Inputs of tens of MB can expand into larger text. VS Code automatically disables some highlighting, folding or language services for large files; the complete indented content remains readable and searchable. The extension does not change global settings. Beyond the extension synchronization size limit, opening the source does not jump to a specific line. See the validation record for 50 MiB measurements and actual test results.

No Webview, network requests or telemetry. Default file associations are unchanged.

Installation and development

Download a released VSIX from GitHub Releases, or package it with the development commands below. In the Extensions panel, choose … → Install from VSIX… and select jsonl-native-reader-0.2.1.vsix. For WSL or SSH files, install the extension in the corresponding remote environment.

Marketplace publication requires the publisher to complete account verification and upload the package. A publisher identifier in a candidate package does not establish that it has been listed.

npm ci
npm run check
npm run build
npm test
npm run bench
node scripts/test-host.cjs
node scripts/ui-smoke.cjs
npm run package

Development uses Node.js 22 and npm. Tests in real VS Code automatically download an isolated 1.96.4 instance and require a graphical display. Test settings and fixtures go under the project’s .file/tmp/ directory. See the validation record for additional checks.

Contributing and maintenance

Report problems through Issues or submit a pull request. Include your VS Code version, file size and a minimal example that can be shared publicly; do not attach private JSONL data. Before making changes, read the architectural constraints in AGENTS.md and run the checks relevant to your changes.

Architecture · Changelog · Publishing guide

Authors and license

Authors: keta1930 and codex-gpt-6-astra.

This project uses the MIT License. Licenses for bundled dependencies are in THIRD_PARTY_NOTICES.md.