What is the real purpose of Base64 encoding?

Solution 1:

Base64 is a way to encode binary data into an ASCII character set known to pretty much every computer system, in order to transmit the data without loss or modification of the contents itself. For example, mail systems cannot deal with binary data because they expect ASCII (textual) data. So if you want to transfer an image or another file, it will get corrupted because of the way it deals with the data.

Note: base64 encoding is NOT a way of encrypting, nor a way of compacting data. In fact a base64 encoded piece of data is 1.333… times bigger than the original datapiece. It is only a way to be sure that no data is lost or modified during the transfer.

Solution 2:

Base64 is a mechanism to enable representing and transferring binary data over mediums that allow only printable characters.It is most popular form of the “Base Encoding”, the others known in use being Base16 and Base32.

The need for Base64 arose from the need to attach binary content to emails like images, videos or arbitrary binary content . Since SMTP [RFC 5321] only allowed 7-bit US-ASCII characters within the messages, there was a need to represent these binary octet streams using the seven bit ASCII characters...

Hope this answers the Question

Solution 3:

Base64 is a more or less compact way of transmitting (encoding, in fact, but with goal of transmitting) any kind of binary data.

See http://en.wikipedia.org/wiki/Base64

"The general rule is to choose a set of 64 characters that is both part of a subset common to most encodings, and also printable."

That's a very general purpose and the common need is not to waste more space than needed.

Historically, it's based on the fact that there is a common subset of (almost) all encodings used to store chars into bytes and that a lot of the 2^8 possible bytes risk loss or transformations during simple data transfer (for example a copy-paste-emailsend-emailreceive-copy-paste sequence).

(please redirect upvote to Brian's comment, I just make it more complete and hopefully more clear).