Base64 is a standard term for numerous comparable encoding schemes that encode binary information from handling it numerically and translating it into a foundation 64 representation. The Base64 term originates from a particular MIME content transfer encoding.
The basic criterion of characters to compose the 64 characters required for foundation varies between implementations. The rule of thumb is to decide on a pair of 64 characters that is both a part of a subset common to the majority of encodings, and also printable. This combination leaves the data unlikely to be altered in transit through systems, such as email, which have been traditionally not 8-bit clean. For instance MIME's Base64 implementation employs A-Z, a-z, and 0-9 for the initial 62 values,"+" and"/" for the previous two. Other versions, generally derived from Base64, share this property but vary from the symbols chosen for the past two values; an example is that the URL and file name protected (RFC 4648 / Base64URL) version, which uses"-" and"_".