base64encoding

Base64 encoding is a binary-to-text encoding scheme that converts binary data into an ASCII string using a 64-character alphabet. It is designed to enable safe transmission and storage of binary data in text-based formats such as email, JSON, and HTML.

The encoding process groups input bytes into 24-bit blocks, subdividing each block into four 6-bit values. Each 6-bit value is mapped to a character in the base64 alphabet (A–Z, a–z, 0–9, +, and /). If the final block contains fewer than 3 bytes, the input is padded with zeros and the output is padded with one or two '=' characters to indicate the number of missing bytes. A URL-safe variant replaces '+' with '-' and '/' with '_', and sometimes omits padding.

Base64 encoding increases data size by approximately one third, producing about 4 encoded characters for every 3 input bytes. It is not encryption and does not provide confidentiality; it is merely a reversible representation that makes binary data text-friendly. The encoding is widely standardized in RFC 4648 and is implemented in many programming environments and protocols.

Common uses include embedding binary data in MIME emails, embedding images or files in HTML or JSON, and transmitting data in URLs or forms where binary content would be problematic. Limitations include increased size, the need for proper padding handling, and the fact that it does not secure the contents. Understanding its characteristics helps in selecting appropriate encodings or variants for different data transmission needs. For reference, a simple example is the string "Hello" encoding to "SGVsbG8=" in base64.