How to find your Mac's serial number
There are several approaches you can take to find your Mac's serial number.
Your Mac's serial number is required for warranty service, among other benefits that Apple offers its customers. Therefore, while not commonly used, you may occasionally need to look it up. While you can always look on your Mac's chassis to find the printed label that contains the serial number, there are a number of additional ways do do this, some of which are more convenient than others.
Besides using the Mac's chassis, the easiest way to find your Mac's serial number is to use the About This Mac information panel that's in the Apple menu. Choose this option, then click the gray version string for your installation of OS X. This will toggle the string between showing the OS version, the OS build number, and your system's serial number.
Clicking the text under the "OS X" label will reveal your Mac's serial number.(Credit: Screenshot by Topher Kessler/CNET)
The next option is to use the System Information utility's "About" panel, which is available by clicking "More Info" in the "About This Mac" panel, or by opening the tool in the Applications > Utilities folder, then pressing Command-i. With this panel open, you can see your Mac's model number and some hardware information in the Overview section, along with your Mac's serial number.
The system information tool also generates an in-depth system report. This is done by clicking the "System Report" button in the About panel, or simply by opening the System Information tool directly from the Finder. In the report, you can click the "Hardware" section (this is the default section), then in the "Hardware Overview" you should see the serial number listed, as well as with other details such as processor, memory, and cache information..... Read Whole Article