Base 64

Base64 is a group of binary-to-text encoding schemes that represent binary data (more specifically, a sequence of 8-bit bytes) in an ASCII string format by translating it into a radix-64 representation. The term "Base64" originates from a specific MIME content transfer encoding.

Overview

Base64 encoding schemes are commonly used when there is a need to encode binary data that needs to be stored and transferred over media that are designed to deal with textual data. This encoding helps to ensure that the data remains intact without modification during transport. Base64 is used commonly in a number of applications including email via MIME, and storing complex data in XML or JSON.

Encoding Process

The Base64 encoding process represents binary data in an ASCII string format by converting it into a base-64 representation. The specific set of 64 characters chosen to represent the 64 place-values for the base varies between implementations. 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. This combination leaves the data less likely to be modified in transit through systems, such as email, that were traditionally not 8-bit clean. The Base64 index table is as follows:

Value	Character
0–25	A–Z
26–51	a–z
52–61	0–9
62	+
63	/

Padding

The output of the encoding process is a multiple of 4 bytes. If the input data is not a multiple of 3 bytes, padding characters are added to the output to ensure its length is a multiple of 4. The padding character is "=".

Applications

Base64 is widely used in various applications including:

• Email via MIME encoding
• Embedding binary data in XML or JSON
• Storing complex data in databases
• Data URL scheme in HTML

Related Pages

• Binary-to-text encoding
• MIME
• ASCII
• Email
• XML
• JSON
• Data URL

See Also

• Base32
• Base58
• Base85