base64

Base64 encoding is widely used and there are nice online tools, for example https://www.base64decode.org/.

On command line could be convenient choice to use openssl with argument base64 to encode or two arguments base64 -d to decode. Tool reads from stdin, or from file with argument -in and writes to stdout or to the file with arguments -out .

echo Blog | openssl base64
QmxvZwo=
echo AB | openssl base64
QUIK
echo QUIK | openssl base64 -d
AB