The Alt key on a Mac is also called the Option key and is located next to the Command key. There are two Alt keys on a Mac keyboard, one on either side of the spacebar. The Alt key is used for many important things on a Mac, such as typing symbols and accent marks, changing the function of another key, and activating program or system shortcuts. The Alt key is also a modifier for menu options and can be used with the arrow buttons to choose from different items. If youre looking for the Alt key on a Mac keyboard, its the third key from the left on the keyboard.