Checking Windows High Contrast Mode on a Mac for free

Caution! This article was published over a year ago, and hasn't been updated since. Situation, software and support of the topic below could have changed in the meantime.

If you are familiar with web accessibility you know that visual disabilities are both prevalent and multifaceted at the same time. It follows that one of the cornerstones of accessibility is making a page adaptable or allowing it to stay adaptable. When you think of these customizations, the first (and only?) thing that probably comes to mind is page and font size zoom. You are aware that both content and functionality should not break when users zoom.

However, zoom and magnification are not the only visual customization users can make. A system-wide change of contrast is quite common as well. For "Windows High Contrast Mode" (WHCM), for example, it is hard to get solid numbers, but that is also a good thing because trying to programmatically recognize assistive technologies or adaptive strategies would be very problematic ethically. Still, Microsoft itself estimates that 60 million people are using WHCM regularly (for more insights, check Martin's article.

From this follows that it is important to test your own pages in Windows High Contrast Mode to check whether they are still readable and usable (or, for example, whether interactive controls are still recognizable as such). Now, a not insignificant part of web developers use Macs (and I'm one of them). This leads to an overrepresentation of Voice Over when it comes to screen reader testing and, at the same time, possibly a lack of WHCM testing in parts of the web dev community.

I usually have a cheap and age-worn Windows Laptop at hand to do just that, but have found a strategy for Windows High Contrast Mode testing that neither needs actual hardware nor financial investment of sorts. In the following, I'd like to share it with you:

  1. Get VirtualBox - in case you are not aware, it is a free and open-source virtualization environment. Of course, other virtualization software on a Mac is available, such as Parallels. But the latter is a commercial product and, thus, not the cheapest option. However, if you have a Parallels licence anyway, you can use it instead of VirtualBox and adapt the following steps as needed (because the overall principle is the same anyway).
  2. Get a Windows 10 virtual machine. Way back when "Edge" was a new Microsoft Browser and established as the successor to Internet Explorer, Microsoft built a page called "" where they supplied Virtual Machines, running various versions of Internet Explorers in various versions in Windows. These machines were available for several environments, among them VirtualBox. While does not exist anymore in its original form, some VMs are still available on
  3. While downloading, write down the Windows admin password stated on this very site because you will be asked for it at every virtual machine startup. Hint: it's Passw0rd!.
  4. When both downloads are finished, launch Virtual Box and select your Microsoft VM. To do that, go to "Machine → Add" in Virtual Box's menu and select the .vbox file you just downloaded.
  5. All Virtual Machines provided by Microsoft expire after 90 days. They themselves recommend doing a snapshot as early as possible so that you can revert to an early state without running into the licence time limit. So start your virtual machine for the first time, remember PasswOrd!, go to the machine's main window on your Mac, and chose "Machine → Take Snapshot" in the main menu
  6. After that, you have a totally normal Windows environment at your disposal. I recommend installing at least the newest Chromium-based Edge browser and Firefox inside the running machine. If you do so, it may be useful to either take another snapshot or postpone the first snapshot to a point in time where your Windows setup, including installed browsers, is complete.
  7. To activate Windows High Contrast Mode itself, click on the search field next to Start button and type "high contrast". I found that to be much more convenient than to click tthough all the menus

From here on, happy checking (and fixing)! Remember that there are 4 High Contrast themes available in Windows 10, "High Contrast Black", "High Contrast White", "High Contrast #1" and "High Contrast #2"

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