The padding character =, used to pad the base64 string to be a multiple of 4, is technically optional as well since they can be inferred from the length, though

The padding character =, used to pad the base64 string to be a multiple of 4, is technically optional as well since they can be inferred from the length, though different decoders can be more strict than others. So virtually all ascii words are valid base64 https://en.m.wikipedia.org/wiki/Base64 https://en.m.wikipedia.org/wiki/Base64 (I got burned by this a few months ago where Chrome can produce HAR files that have base64 encoded bodies without padding characters, and .NETs built in decoder expects them)