As I repeatedly (e.g. every 2nd year) have to find the right code to generate a HMAC SHA256 hash from a string, I’m sharing this (for me and others) here. The tricky part is the String-Format to 64 chars. Most code I’ve found had this set to 32 chars (like used for MD5) which resulted in too short hashes for certain inputs.

I hope you find this useful!