Do you need to find the serial number on your Mac? Serial numbers were added by Apple to provide better service to its customers. They’re generally used for warranty purposes, but they can also help prevent theft.
There are a few different ways to find your Mac’s serial number. I’m going to sort these methods from easiest to hardest, but they all work perfectly well:
Easy method: Apple Menu > About This Mac. From here, click on the Version number, which should say something like Version 10.9.1. On the first click, the Version number will change to your Build number, and on your second click, it will show your serial number.

Slightly less easy method: Apple Menu > About This Mac > More Info… > System Information > About

Still pretty easy method: The main reason this wasn’t at the top of the list was because it involves leaving your office chair. Your Mac’s serial number is printed on the outside case of your device. The exact location varies depending on your device. On Mac laptops, it will be found in small print on the bottom, while iMacs have it on the base of the system that’s facing the desk. You’ll also find this unique code on the box your Mac came in.

Kinda hard method: Feel like showing off to your friends? You’ll want to use this method, which involves using the OS X Terminal. The only other reason you’d use this method is if you were logged into a system remotely. Say, via SSH. Simply type the following system_profiler code into the Terminal to reveal the Serial Number.
system_profiler SPHardwareDataType | grep Serial
Serial numbers are unique to your Mac. Don’t share your serial number online or show it to other people. It’s a valuable piece of identification and could make the difference between Apple Support covering for you or calling you a thief. Use this power wisely.