One variation to the standard Caesar cipher is when the alphabet is "keyed" by using a word. In the traditional variety, one could write the alphabet on two strips and just match up the strips after sliding the bottom strip to the left or right. To encode, you would find a letter in the top row and substitute it for the letter in the bottom row. For a keyed version, one would not use a standard alphabet, but would first write a word (omitting duplicated letters) and then write the remaining letters of the alphabet. For the example below, I used a key of "rumkin.com" and you will see that the period is removed because it is not a letter. You will also notice the second "m" is not included because there was an m already and you can't have duplicates.

This encoder will let you specify the key word that is used at the beginning of the alphabet and will also let you shift the keyed alphabet around, just like a normal Caesar cipher. This is similar to the rot13 cipher, and can also be performed with the cryptogram solver. A simple test to see how this works would be to insert the alphabet into the encoder and then change "Shift" and modify the key.

This is your encoded or decoded text: