ARCHIVED: In MIME, what is the Base64 encoding method?

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Base64 is an encoding method that is used primarily to transfer binary attachments over the Internet. If you looked at the contents of a Base64 file, it would appear to contain many lines of seemingly random numbers and letters. It is similar to UUencode and BinHex in that it encodes files into ASCII (text) format, making them less susceptible to corruption as they are passed through Internet gateways. However, it was designed to be more stable and effective than these binary-to-text encoding methods and is based on the printable encoding method first introduced with PEM (Privacy Enhanced Mail). As with other binary-to-text encoding methods, files encoded with Base64 will be larger than the originals. The increase in file size is typically about 33%.

All MIME-compliant clients are capable of decoding Base64, but their ability to display or otherwise use the resulting file depends on both the client and the content of that file. There are also a number of stand-alone applications that will decode Base64 content, notably metamail and mpack. For more information about Base64, see RFC 2045, section 6.8, available at:

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Last modified on 2018-01-18 12:05:35.

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