Base 64 Encode / Decode is a tool that can be used to encode/decode data.

Base64 encoding is designed to make binary data survive transport through transport layers that are not 8-bit clean, such as mail bodies.
Base64-encoded data takes about 33% more space than the original data.

The term Base64 refers to a specific MIME content transfer encoding. It is also used as a generic term for any similar encoding scheme that encodes binary data by treating it numerically and translating it into a base 64 representation. The particular choice of base is due to the history of character set encoding: one can choose 64 characters that are both part of the subset common to most encodings, and also printable. This combination leaves the data unlikely to be modified in transit through systems, such as email, which were traditionally not 8-bit clean.

The w3dt Base64 encode/decode tool is based off code by David Nedved.