Base64 encode/decode

Base64

The term Base64 encoded string is coming from a certain MIME content transfer. Base64 string is a collection of related encoding designs which represent the binary information in ASCII format by converting it into a base64 encoded representation.

Base64 encoding schemes are basically used when there is a need to store or transfer encoded binary information or media files that are developed to deal with textual information. This guarantees that the data stays unchanged without modification during transfer. Base64 is generally used in a number of applications including electronic mail via MIME, and keeping complex information in XML.

The special 64 characters chosen for the base can vary among implementations. The popular theory is to select a set of 64 characters that is both part of a subset typical to most encodings. This combination leaves the data impossible to make alternation in transportation through information systems, such as electronic mail, that were typically not 8-bit clean. The Base64 implementation in MIME uses a-z, A-Z and 0-9 for the first 62 values. Other Base64 modifications share the same property but they use different symbols in the last two values.

Base64 index table:
 

Source: Base64 on Wikipedia