crypt.base64decode

Decodes a Base64-encoded string back to raw bytes. Reverses the encoding process: each group of 4 Base64Base64A binary-to-text encoding that represents binary data as ASCII characters. Every 3 bytes become 4 characters from the alphabet A-Z, a-z, 0-9, +, /. Padding with = if input length isn't divisible by 3. characters maps back to 3 bytes of original data:

Base64 chars:  S  G  V  s  b  G  8  =
6-bit values:  18 6  21 44 27 6  60 (pad)
Reassembled:   0x48 0x65 0x6C 0x6C 0x6F
Output:        "Hello"

The = padding characters indicate the final group had fewer than 3 bytes. Accepts standard Base64 alphabet (A-Z, a-z, 0-9, +, /).