How to decode signature part of JSON Web Token

The signature is indeed base64url encoded and you can decode it. But the result is a numerical value which is not meant to be printed. You can decode with a base64url library and view the value in your program. The result is a byte array which represents the hash value calculated with header, payload and secret as an input.

As it is a C# question and you asked how to decode it, here's a code snippet that does the conversion manually without any extra libs:

string signatureBase64UrlEncoded = "xlQ7tk_LADnw2whWVafyKCBc9cPKIRSSQo2kVxbynCA"; string signatureBase64Encoded = signatureBase64UrlEncoded .Replace('_', '/').Replace('-', '+'); switch (signatureBase64Encoded.Length % 4) { case 2: signatureBase64Encoded += "=="; break; case 3: signatureBase64Encoded += "="; break; } var decodedSignature = System.Convert.FromBase64String(signatureBase64Encoded); 

The code to convert the signature from base64url to base64 encoding is taken from Mark Gravell's answer here

The decodedSignature is a byte array:

Maybe this answer is interesting for you, as it explains how to create the signature and convert the values to base64url encoding.