Testing a used Mac – list of helpful tips and apps

If you buy a used Apple computer or accessories for it, you may want to test whether everything works as well as it was advertised. Does the Mac have as much hard drive space as stated? Is there really that much RAM installed? Does the display of the iMac or MacBook have any errors? Does the built-in or included keyboard work properly? These and several other factors can be controlled. Sometimes a simple look at the system information is enough, sometimes software can help with the check. Below you will find a few tips and apps.

Note: The article does not claim to be complete. So if you have a few tips and test apps up your sleeve, please leave a comment :)

Checking a used Mac: here you will find a few simple measures to check information from the sales offer and try out individual components.
Checking a used Mac: here you will find a few simple measures to check information from the sales offer and try out individual components.

You can test these things immediately (if you buy them on site).

If you don't order the used Mac online via classifieds or eBay, but can pick it up in person and try it out on site before buying, you should take advantage of this option. Here are a few things that you can try out straight away - depending on the situation and patience of the person selling:

  • General check for damage: Look at the Mac, the charging or power cable, the power adapter, the keyboard and mouse, or whatever else was included to identify possible damage. But first look at the offer to see whether these damages have already been mentioned. If so, there is nothing to complain about.
  • Test power supply: Most Mac models will not turn on if there is something wrong with the power supply. A MacBook with a built-in battery, on the other hand, can work even if the connected power adapter does not supply power or the connection on the device is damaged. So turn on the MacBook and navigate (if possible) to a view in which you can check whether the battery is charging and the laptop is running on mains power.
  • Switch on and check display: If it is an iMac or a MacBook, you can determine immediately after switching on whether the display is working, whether it has any damage, whether the backlight / maximum brightness is sufficient, etc.
  • Check whether a firmware password is set up: Ideally, the person selling has cleaned up the Mac's memory and installed a fresh macOS installation. If the welcome screen appears, which allows you to set up the system again, that's a good sign. However, the Mac asks for one after switching on Firmware password, then hopefully the person has this on hand (and can then disable it via recovery mode). You can read how you, as the legal owner of a Mac, can have the firmware password removed in the Apple Store here: Reset Mac Firmware Password: Experience report from the Apple Store.
  • Testing without third-party apps: If you can set up the Mac on site and therefore have access to macOS and its settings as well as pre-installed apps, then you can carry out some of the tests described below or determine individual information in order to compare it with the information in the sales advertisement.

The right hardware: About this Mac, System Preferences and System Report

The first step should be to look at the “About This Mac” window, which you can access via the Apple logo in the menu bar (top left). There you will find the exact name of the Apple computer, its year, the installed processor (e.g. Intel CPU) or system chip (e.g. M1, M2 or M3), next to “memory” the size of the RAM and so on. On Intel Macs there is also a line for the graphics chip (GPU). You can also view the serial number there and, if necessary, compare it with the information on the invoice. Finally, you will be shown which macOS version is installed.

Until macOS 12 Monterey, the “About this Mac” window still had various tabs. You could use this to find out more about the display, the hard drive and the support status. There was also a tab for information material, such as a link to the online data sheet of the Mac used. All of this stuff has been moved to the system settings starting with macOS 13 Ventura. There is now a “More Info” button in the “About this Mac” window. If you click on this, you will land in the area General -> Info the system settings. There you will find the data shown above again, but also information about the size of the mass storage (Macintosh HD), information about the display, etc.

You can go into further detail by either interacting with one of the buttons in the individual areas or by clicking on the “System report…” button at the bottom. Here we come into a quite technical area. However, the first list item called up is “Hardware”. And there you will find more detailed versions of the information above. For example, the model identification of your Mac, the model number, and for M-chips the number of Performance and efficiency cores, firmware versions and much more. If you click on another list item (left), you will receive a lot more information (right). This way you can check numerous components of your Mac.

Check individual components: Inspect app tests keyboard and display

The free and open source Inspect app that you here at GitHub You can download it, Jens recently did presented in the forum. Although it hasn't been updated for a few years, it still works perfectly under the latest operating systems (currently macOS Sonoma). After installing from the dmg file and starting the app, you can choose between a keyboard test and a dead pixel test.

If you click on the “Keyboard Test” in the Inspect app, a window with a keyboard graphic will be displayed. Although this has a QWERTY layout, you can still test QWERTZ or other layouts with it. If you press a key, it will be marked - if it works. If you press a key and it is not highlighted in color, then it could be broken or at least stuck. By the way, the keyboard test can be used for external keyboards (both Apple's Magic Keyboard and third-party keyboards) as well as for internal keyboards of the MacBook.

If you click on the “Dead Pixel Test”, the display or external monitor on which the app window is located will be filled with a single color. The first is red. Then use the arrow keys to display green, blue, white, black, cyan, magenta and yellow. To leave the full-display view, press the escape key (esc). There is no automatic analysis of the display or monitor, but you can search for individual dark, light or simply different colored points in the color areas. In this way, pixel errors can be detected and dead pixels can be identified.

Test the read and write speed of different storage media

Regardless of whether it's internal mass storage, external hard drives or USB sticks - with the Blackmagic Disk Speed ​​Test app you can determine the read and write speeds of these storage media or the USB ports through which they are connected. The app should not be confused with the Blackmagic RAW Speed ​​Test app, which comes with DaVinci Resolve is installed. You can find the Blackmagic Disk Speed ​​Test app as a free offer in the Mac App Store. After installation, you can start the test using the “Speed ​​Test Start” button. There is also a gear button above it, which you can use beforehand, for example. B. you can select another storage medium, i.e. the external hard drive or USB stick.

Try out individual components and functions

If the Mac comes with accessories (keyboard, trackpad, mouse, webcam, etc.), then these can and should of course be tried out - at least if they are to be used. Functionality is anything but guaranteed, especially with vintage computers and their accessories. You can and should also try out built-in hardware, such as the webcam on the iMac or MacBook. To do this, you can open the app called Photo Booth that is preinstalled in macOS. This goes over very quickly Spotlight (command+spacebar), via the Launchpad or the Applications folder.

Your tips for checking used Macs

Do you have any hints, tips and app recommendations to add to this post? Then feel free to leave a comment accordingly!

>>> What is a Legacy Mac and where can you get it repaired? <<

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