C# Decode JWT

This guide provide insights on decoding JWT in C#. The snippet below demonstrates a practical example of JWT decoding using C#.

private static void DecodeJwt(string token, string key)
    var secretKey = Encoding.UTF8.GetBytes(key);
    var validationParameters = new TokenValidationParameters
        ValidateIssuer = false,
        ValidateAudience = false,
        ValidateLifetime = true,
        ValidateIssuerSigningKey = true,
        IssuerSigningKey = new SymmetricSecurityKey(secretKey)

    var principal = new JwtSecurityTokenHandler().ValidateToken(token, validationParameters, out var validatedToken);

This C# snippet decodes a JWT (JSON Web Token). It uses a method called DecodeJwt, which accepts the JWT token and a key as parameters.

The key is converted to a byte array using UTF8 Encoding. A new TokenValidationParameters object is created with necessary validation flags set to true. The IssuerSigningKey is produced by the byte array.

Finally, the ValidateToken method of JwtSecurityTokenHandler is used to validate and decode the JWT. The decoded token is stored in a variable called principal.