Equip Compare

EquipCompare is an addon that provides the basic feature of comparing equipment currently equipped against equipment anywhere else in the game. It's surprising this feature is only provided in some locations by Blizzard's default user interface. With EquipCompare you can enable it everywhere.

EquipCompare also lets you compare equipment with equipment equipped on characters that you aren't playing . To do this you'll need to install an addon called CharactersViewer. Through that addon you can select the alternative character. Then when you're viewing an item it will show their item when comparing. You can shop for your alts with your mains which is otherwise a daunting task.

Another reason to use EC is to help monitor your equipment and ensure that you didn't accidentally equip something. This one time, I realized that I had accidentally equipped a trash item from questing. I realized how bad it was when EquipCompare showed me the gray item and helped me realize the error.