JWT Decoder

A command-line tool for decoding and inspecting JSON Web Tokens (JWT) with a beautiful, colorful terminal UI powered by Spectre.Console.

Features

• 🔓 Decode JWT tokens without requiring the signing key
• 🎨 Beautiful color-coded output for header, payload, and signature
• ⏰ Automatic parsing of common JWT claims (exp, iat, nbf)
• ✅ Expiration status checking with visual indicators
• 📋 Pretty-printed JSON output

What It Does

JWT Decoder takes a JWT token string as input and:

1. Decodes the header - Shows the token type and signing algorithm
2. Decodes the payload - Displays all claims in formatted JSON
3. Shows the signature - Displays the Base64 URL-encoded signature
4. Analyzes timestamps - Converts Unix timestamps to readable dates and highlights if the token is expired

NuGet Packages Used

This project uses the following NuGet packages:

• Spectre.Console (v0.54.0) - Rich terminal UI framework for beautiful console output
• Spectre.Console.Cli (v0.53.0) - Command-line parsing and execution framework
• Spectre.Console.Json (v0.54.0) - JSON syntax highlighting for terminal output

Prerequisites

• .NET 10.0 SDK or later

Building the Project

Debug Build

dotnet build

Release Build

dotnet build -c Release

Publishing

Publish as Self-Contained Executable

To create a standalone executable that includes the .NET runtime:

dotnet publish -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true

The executable will be generated at:

JwtDecoder\bin\Release\net10.0\win-x64\publish\JwtDecoder.exe

Publish as Framework-Dependent

For a smaller executable that requires .NET 10.0 to be installed:

dotnet publish -c Release -r win-x64 --self-contained false

Adding to PATH

To use the JwtDecoder command from anywhere in your terminal:

Option 1: PowerShell Profile (Recommended)

1. Open your PowerShell profile:

   notepad $PROFILE

2. Add the publish directory to your PATH:

   $env:Path += ";C:\Privatespace\Labb\JwtDecoder\JwtDecoder\bin\Release\net10.0\win-x64\publish"

3. Save and reload your profile:

   . $PROFILE

Option 2: System Environment Variables (Permanent)

1. Open System Properties:

   • Press Win + X and select "System"
   • Click "Advanced system settings"
   • Click "Environment Variables"

2. Under "User variables" or "System variables", find and select Path, then click "Edit"

3. Click "New" and add the publish directory path:

   C:\Privatespace\Labb\JwtDecoder\JwtDecoder\bin\Release\net10.0\win-x64\publish
   

4. Click "OK" to save changes

5. Restart your terminal for changes to take effect

Option 3: Create an Alias

Add an alias to your PowerShell profile:

Set-Alias jwt "C:\Privatespace\Labb\JwtDecoder\JwtDecoder\bin\Release\net10.0\win-x64\publish\JwtDecoder.exe"

Usage

Once installed, decode a JWT token by passing it as an argument:

JwtDecoder <your-jwt-token>

Example

JwtDecoder eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

Note: If you don't supply a JWT token as an argument, the tool will automatically read it from your clipboard. This feature was contributed by @Fjeddo.

This will display:

• A color-coded header section showing the algorithm and token type
• A formatted payload with all claims
• The signature in Base64 URL encoding
• A table showing important timestamps (expiration, issued at, not before)

Development

The project structure:

• Program.cs - Entry point that sets up the CLI application
• DecodeCommand.cs - Main command implementation with JWT decoding logic

License

This project is provided as-is for educational and development purposes.