What is Base64?

Base64 is a way to represent any binary data as plain ASCII characters (A–Z, a–z, 0–9, plus + and /). It is widely used to embed images in CSS or HTML (data: URIs), to send binary payloads in JSON, and to encode credentials in HTTP Authorization headers.

Base64 is not encryption. Anyone with the encoded string can decode it back trivially. Use it for transport, never for secrecy.

URL-safe Base64

Standard Base64 uses + and /, which have special meaning in URLs. URL-safe Base64 (RFC 4648 §5) replaces them with - and _, and usually drops the trailing = padding.