Decode and Encode Base64 using Mac OSX terminal

Starting with version 10.8 Mac OSX ships with built-in utility base64.

Decoding Base64 string to text

$ echo -n "VGhpbmsgZGlmZmVyZW50" | base64 -D
> Think different

Encoding Base64 string

$ echo -n "Think different" | base64
> VGhpbmsgZGlmZmVyZW50

Note that without -n parameter echo will produce a string with a new-line character added to its end.

You also have an option to use pbpaste utility which basically returns contents of your clipboard:

$ pbpaste | base64
> VGhpbmsgZGlmZmVyZW50

Encoding Base64 string from file

base64 utility supports encoding binary files:

$ base64 -i icon.svg
> PHN2ZyByb2xlPSJpbWciIHZpZXdCb3g9IjAgMCAyNCAyNCIgeG1sbnM9Imh0dHA6...

You might want to copy the result of encoding into your clipboard without need to manually select the resulting string with use of pbcopy command:

$ base64 -i icon.svg | pbcopy