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Your Mac, iPhone, and iPad all have a Universally Unique Identifier (UUID) assigned. These codes are specific to each device and, similar to a serial number, they are used by developers to identify each one individually. Here's what you need to know.
What is a UUID?
A UUID is a string of letters and digits that forms a unique pattern. Your Mac, iPhone, and iPad each have one UUID, and no other device shares it. It's similar to a serial number in that regard, but whereas serial numbers are used to identify your device by Apple and your cellular carrier, developers usually use the UUID instead.
Normally, you wouldn't need to know (or access) your UUID. But if you're registering a device as part of the Apple Developer Program so you can install beta software, you'll need it. App developers might also ask for your device's UUID so that they can provide builds that will only work on that particular device.
How to Find Your Mac's UUID
Click the Apple logo in the menu bar, and then click the "About This Mac" option.
Click the "System Report" button.
Note the text beside Hardware UUID.
You can copy the text directly from the window, if necessary.
How to Find Your iPhone and iPad's UUID
Connect your iPhone or iPad to your computer, and then open iTunes. Click the device icon at the top.
Your device's UUID is hidden by default---click "Serial Number" and it will change to display your UUID.
You can also copy the UUID directly from within iTunes.
Other identifiers to Note
There are some other identifiers that you might come across, as well.
- Model Identifiers are used to highlight which model a particular device is. These aren't unique to that device, but rather, the model band that it falls into. For example, an iPhone 7 is known as iPhone9,x, whereas an iPhone XS is iPhone11,x. These numbers are normally only used by Apple, but sometimes they appear in leaks about upcoming devices.
- Apple and its suppliers use model numbers to identify devices and the market for which they are designed. For example, an iPhone XS sold in the United States is A1920, whereas one sold in Japan is A2098.
- IMEI numbers, also known as International Mobile Equipment Identify numbers, are used by carriers. They're unique to any device that connects to the cellular network and are often used to block devices that have been reported as stolen or lost.