See also https://en.wikipedia.org/wiki/Base64#Variants_summary_table https://en.wikipedia.org/wiki/Base64#Variants_summary_table. base64url is common, with - an

See also https://en.wikipedia.org/wiki/Base64#Variants_summary_table https://en.wikipedia.org/wiki/Base64#Variants_summary_table. base64url is common, with - and _ instead of + and /. As for concatenating, that’s not valid even in variants where = padding is mandatory: padding marks the end and is not allowed to occur mid-string. But I don’t think this is a problem, either: transparently concatenating Base64 strings is not generally a useful operation; I can’t think of any valid use case for it off the top of my head, I’m curious why you might think it useful. Base64 is a transfer encoding sort of a thing, and concatenating blobs while in their transfer encoding just… isn’t something that you do.