Decode On Copy tries to base64 decode any text that you copy, and if it can be decoded to a valid URL, the URL will be copied to your clipboard instead. It is best demonstrated by example.
The simplest case is where you copy something that is not an encoded URL, like http://www.example.com. Since the text you copied can't be decoded to a valid URL, you will end up with http://www.example.com on your clipboard.
Now, if you copy aHR0cDovL3d3dy5leGFtcGxlLmNvbQ==, Decode On Copy will notice that it can be base64 decoded to http://www.example.com and will copy http://www.example.com to your clipboard instead of aHR0cDovL3d3dy5leGFtcGxlLmNvbQ==.
Decode On Copy can also detect URLs that have been base64 encoded multiple times. So copying YUhSMGNEb3ZMM2QzZHk1bGVHRnRjR3hsTG1OdmJRPT0= would also result in http://www.example.com being copied to your clipboard.
