Readers often write in to ask which model of Mac they own. This lets them understand which features are built-in and whether their model qualifies for certain upgrade or connection options. With iMac owners, that’s often whether the iMac is of the right vintage (2009 to early 2014) to act as an external monitor for another Mac via Target Display Mode.

Apple has several ways of identifying a Mac, each of which is found in a different location or by another method. Most items are found in About This Mac ( > About This Mac) or System Information (hold down Option and choose  > System Information). Other details may require using a web-based lookup, consulting a web page, or looking at the tiny print on your Mac on the back or underside.

Here’s how to find your Mac model.

Serial number

Every Mac has a serial number that uniquely defines it. It’s shown in About This Mac’s main screen and in the Hardware Overview in System Information. Your serial number helps you obtain warranty service. You can use the serial number in the AppleCare coverage lookup page on Apple’s site to also find out the human-readable model name described next. The serial number is also printed on nearly all Macs (on an iMac, it can be on the underside of its stand) and available via the Apple ID site for devices registered to your account.

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Model name

About This Mac’s first line of detail tells you the model number; within parentheses, macOS offers other details; Apple calls this “Tech Specs” on its site, as on this page on identifying MacBook models, but nowhere else. My iMac shows up as “iMac (Retina 5K, 27-inch, 2017)”. That’s usually enough information to find out from third-party sites that offer instructions on upgrades or repairs what parts or tools you need. It also conforms to how Apple often lists models that qualify for the latest version of macOS and for extended warranties (such as replacing a keyboard in a laptop). Oddly, the Apple ID site doesn’t list the complete model information—only the general details, like “iMac 27ʺ 5K”. (The type of memory required is also listed, like “64 GB 2400 MHz DDR4”, useful if you have a Mac that supports adding third-party memory.)

Model identifier

It’s sometimes helpful to find the “shorthand” number that more concisely describes your Mac. Use System Information for that. The Hardware Overview that appears by default in the main screen of System Information shows the Model Identifier in the second line. Mine appears as “iMac18,3” with no spaces.

Marketing part number

Apple assigns a part number to its devices that can define the country for which it manufactured a particular configuration of hardware or a combination of characteristics, like the difference between a space gray and gold MacBook Air. This number is printed on a Mac and on the packaging that came with it. It looks like MGND3LL/A (a 13-inch M1-based 2020 MacBook Air in gold).

Model number

If that’s not enough, Apple also assigns a model number to its Macs. This number may be used for a single edition of Macs based on CPU and other factors or might span a dozen or more distinct versions of model line. EveryMac offers insight on this topic—which is that it’s impossible to know Apple’s choices here. Models numbers (sometimes called “family numbers”) look like A2179. They’re printed on your Mac.

Ask Mac 911

We’ve compiled a list of the questions we get asked most frequently, along with answers and links to columns: read our super FAQ to see if your question is covered. If not, we’re always looking for new problems to solve! Email yours to mac911@macworld.com, including screen captures as appropriate and whether you want your full name used. Not every question will be answered, we don’t reply to email, and we cannot provide direct troubleshooting advice.