Here’s the detailed report from Mozilla Research: Over the Edge: How Microsoft’s Design Tactics Compromise Free Browser Choice (PDF, 5MB, 74 pages)

And the announcement post from Mozilla Research referenced in the The Register’s article is here:

Over the Edge: The Use of Design Tactics to Undermine Browser Choice

In order to be able to choose their own browser, people must be free to download it, easily set it to default and to continue using it – all without interference from the operating system. Windows users do not currently enjoy this freedom of choice.

To investigate Microsoft’s tactics and the impact on consumers, Mozilla commissioned Harry Brignull and Cennydd Bowles, independent researchers and experts in harmful design. Today, the researchers have published a report detailing how Microsoft prevents effective browser choice on Windows. In the report, they document how Microsoft places its own browser — Edge — at the center of its operating system and weaponizes Windows’ user interface design to undermine people selecting rival browsers.

In some cases, the use of harmful design tactics is contrary to Microsoft’s own design guidelines. In many cases, it can lead to (and exacerbate) consumer harm and undermine competition from rival browsers. This kind of behavior is particularly concerning for an independent browser like Firefox, which is reliant on the operating systems provided by companies who are also rival browser vendors.

Self-preferencing from operating system/browser providers is an area Mozilla has previously highlighted, for example, in the Five Walled Gardens report. Recently, details of many issues Mozilla experiences competing on major operating systems were published on the Platform Tilt dashboard.

Now, with the implementation of the Digital Markets Act in the European Union marking the start of a wave of global competition regulation, we hoped that the barriers to browser competition would be dismantled. However, even where there is movement in the right direction, improvements have been incomplete and are grudgingly offered only in markets where regulators have forced platform owners to make changes to respect browser choice. For example, Apple’s decision to allow alternative browser engines is only effective in the EU.

Similarly, Microsoft recently pledged to stop some of the actions it takes to force Edge on users who have selected other browsers. Unfortunately, these changes only address a small number of the tactics outlined in this report. And, to make matters worse, they will only be deployed to users in the EEA.

Windows users everywhere, especially in the rest of the world, continue to have their choices inhibited, overridden and undermined by Microsoft’s use of harmful design. Regulatory action around the world is needed to restore browser choice and competition across all of the major platforms.

Download the full report (PDF, 5MB, 74 pages)