Base64 Decoder

Decoding Base64 reverses the encoding process: it reads the 64-character alphabet back into 6-bit groups, reassembles them into 8-bit bytes, and drops any padding characters, recovering the original data exactly as it was before encoding. Because the process is entirely mechanical and requires no secret key, decoding is always a one-step, deterministic operation — there's no 'wrong' way to decode valid Base64, only valid or invalid input.

This is commonly needed when working with things like JWT segments, Basic Auth headers (Authorization: Basic <base64>), data URIs, or values pulled from a config file or API response that were encoded for safe transport. Pasting the encoded string here immediately shows what it actually contains, without needing to write a script or open a REPL.

A common point of confusion is mistaking Base64 for a security mechanism — since decoding requires no password or key, Base64-encoded data offers no confidentiality at all. If the decoded output isn't readable text, the original data was likely binary, such as an image or compressed file, rather than plain text, which is expected and not an error.