Often in the info world you’ll run into plenty of Base64 encoded strings. A typical giveaway is the trailing = or == in many cases.
base64 -i <file>
base64 -di <file>
-i : Useful for ignoring garbage.
-d : Decode, without this flag it will encode.
Example – Encoding Base64
echo The quick brown fox jumped over the lazy dog> encode.txt
base64 -i encode.txt
Example – Decoding Base64
echo VGhlIHF1aWNrIGJyb3duIGZveCBqdW1wZWQgb3ZlciB0aGUgbGF6eSBkb2cuLi4=> decode.txt
base64 -di decode.txt
>> The quick brown fox jumped over the lazy dog…
Obviously you can also do this without going via a file directly on the command line with piping.