Unlike Video mirroring, video spanning allows a Macintosh's desktop to expanded beyond one monitor. Different information is viewed on the different displays, hence a more capable graphics card is normally required than when using video mirroring.
When you are using video spanning, your menu bar will only appear on one display. The monitor that hosts your menu bar is the primary display.
Not all Macintosh models (including laptops) support video spanning, even if they handle video mirroring. Typically, a computer which can perform video spanning can also provide video mirroring. In order to support video spanning, a machine must have:
- a single graphics card which is capable of providing different information to multiple monitors, or
- two or more video cards installed in the same computer, and compatible software drivers for the cards.
In either case, the setup for video spanning is within the Monitors control panel under the "Apple Menu" in "Mac OS classic" or within the Displays panel under the System Preferences application in Mac OS X.