JWT Preview

A Visual Studio Code extension for viewing JWT token contents in a clear, readable format. Paste a token or select one in the editor to inspect its Header and Payload as readable JSON, with standard claims formatted for quick reading.

Privacy

No telemetry. No network requests. Tokens are never stored.

Decoding happens on your machine, inside a webview whose Content Security Policy blocks network access entirely (default-src 'none', connect-src 'none'). The extension has no runtime dependencies, reads the clipboard only when you press the paste button, and does not retain any data after the panel is closed.

Features

• Live decoding as you type or paste.
• Header and Payload rendered as a collapsible JSON tree; the Signature segment is displayed as-is.
• Standard claims formatted where present: exp, iat, nbf, iss, sub, aud — with UTC timestamps, relative times, and expiration status.
• Correct Base64URL and UTF-8 handling, including non-Latin characters.
• Follows the editor theme (light, dark, high contrast).

What it does not do

The extension does not verify signatures — that would require the signing key or secret. It decodes and displays token contents only. A decoded token tells you nothing about whether the token is authentic or trustworthy.

Usage

Open the Command Palette (Ctrl/Cmd+Shift+P), run JWT: Open Preview, and paste a token into the input field.

To decode a token that is already in your editor: select it, right-click, and choose JWT: Decode Selected Token.

Installation

Install "JWT Preview" from the Visual Studio Code Marketplace, or download a .vsix from the repository's Releases page and install it via Extensions: Install from VSIX....

Feedback and security

• Bugs and feature requests: GitHub Issues
• Security issues: see SECURITY.md — please never include real tokens in reports.

Development

npm install
npm run compile   # compile TypeScript to out/
npm run watch     # compile in watch mode
npm test          # run the test suite
npm run package   # build the .vsix

To run the extension for testing, open this folder in VS Code and press F5 (Extension Development Host).

License

MIT — see also the changelog.