You can use the About This Mac window to find your computer’s serial number. In the About This Mac window, if you click twice on the Mac OS X version number, it will display the serial number. Another method is to use the System Profiler.
1. From the menu bar, click on the Apple logo and then click on About This Mac
2. The About This Mac window will open, click on the OS X Version number
3. The first click will display to you the Mac Build number
4. Click once again, and the serial number will be displayed. However, if you want to copy this serial number, you will not be able to select and copy it.If you clicked once again, the MAC OS X version number will be displayed again
5. If you want to copy this serial number, then click on More Info…
6. Under the Overview section, the Serial Number is displayed and in this window you can select and copy the Serial number.
7. Another place where you can copy the serial number is by clicking on the System Report… butt
and then the Serial Number will be displayed where you can copy it from this window as well.
You can find the serial number of you Mac computer without moving from your chair. You don’t need to flip your Mac laptop or go and look on its back if its an iMac or Mac Pro, you can find the serial number from inside the OS X operating system itself either from the About This Mac window or the System Profiler.