Base64like

Base64like is an informal term used to describe encodings that resemble Base64, in which binary data is converted into an ASCII string using a 64-character alphabet. Like standard Base64, the encoding typically processes input in 3-byte blocks and produces 4 ASCII characters, using padding with equals signs to reach a length that is a multiple of 4. The usual character set includes A–Z, a–z, 0–9, and two additional symbols, commonly a plus and a slash in the standard variant.

Variants differ in the exact alphabet and padding rules. The URL-safe variant substitutes hyphen for plus and underscore for slash, making the result safe for inclusion in URLs and filenames. Some implementations omit padding entirely or omit line breaks, producing a shorter string at the cost of requiring the decoder to be aware of the variant. MIME-based Base64 may insert line breaks every 76 characters, whereas compact forms used in data URIs or tokens often avoid such breaks. In addition, some environments use custom or localized alphabets for compatibility with specific systems.

Common use cases involve encoding binary data for text-based channels, such as email or JSON-based protocols, embedding images or files in textual formats, and transporting binary payloads in tokens like JSON Web Tokens (which rely on a URL-safe, padding-optional variant). It is important to note that base64like encodings are not encryption and do not provide confidentiality; they simply encode data to ensure safe transport and textual compatibility.

The term base64like remains informal and context-dependent; many projects simply refer to their specific base64 variant (standard base64, base64url, or a custom alphabet) rather than using the umbrella label.