If you follow rfc4648, those are "base 64" but not "base64": > This encoding [using '-' and '_'] may be referred to as "base64url"... Unless clarified otherwis

If you follow rfc4648, those are "base 64" but not "base64": > This encoding [using '-' and '_'] may be referred to as "base64url"... Unless clarified otherwise, "base64" refers to the base 64 in the previous section ['+' and '/'].