What is Base64 Decoder?
Base64 decoding is the reverse of Base64 encoding — it converts a Base64-encoded ASCII string back into the original binary or text data. This is frequently needed when inspecting JWT tokens (the header and payload are Base64url-encoded JSON), debugging HTTP Basic Authentication (the Authorization header contains Base64-encoded credentials), analyzing email attachments (MIME encodes binary attachments as Base64), and examining data URIs embedded in HTML or CSS. Base64url is a variant that replaces + with - and / with _ to make the encoded string safe for use in URLs and filenames without percent-encoding.