Veteran browser maker Opera has filed a complaint with Brazil's Administrative Council for Economic Defense (CADE) against Microsoft over alleged anti-competitive practices in Windows that favor Edge.

The complaint alleges that "all-or-nothing" bundled rebates force PC manufacturers to make Edge the "exclusive" pre-installed default browser and that Microsoft employs "dark pattern tactics" including ignoring default browser choices in some scenarios and stopping users from switching away from the defaults on Windows "S mode" devices.

Windows S mode is a locked-down version of Windows. Only apps from the Microsoft Store are allowed, and Edge is used for browsing. For Windows 11, it can only be used in the Home edition.

Users can switch out of S mode, unless blocked by their organization. However, [1]according to Microsoft , "switching out of S mode is one-way. If you switch out of S mode, you'll need to keep using the standard version of Windows 11."

Brazil is an important market for Opera, although the browser's market share has been declining slightly over the last few months, according to [2]StatCounter . It currently stands at 6.78 percent, compared to Edge's 11.52 percent and Chrome's 74.95 percent.

Worldwide, Opera has a market share of 2.65 percent.

If this sounds a lot like a demand for the [3]browser choice screen that Microsoft was forced to implement over a decade ago in response to complaints about Internet Explorer's dominance, you'd be right.

[4]

Aaron McParlan, General Counsel at Opera, told The Register : "Opera believes that Microsoft should, among other things, show a browser choice screen, just as it has done in previous years in the European Union. This choice screen should be presented to all users in a user-friendly and unbiased format and include the main available PC browsers in Brazil."

[5]

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Edge is not as dominant as Internet Explorer once was. Google's Chrome rules the roost these days, and we wondered why Opera was not also targeting Chrome with its complaint.

[7]Windows 10 turns 10: Dying OS just worked, lacked compatibility chaos

[8]Microsoft bolts Copilot Mode onto Edge to chase AI-browser crowd

[9]Massive browser hijacking campaign infects 2.3M Chrome, Edge users

[10]Microsoft will stop pestering Windows users about Edge in EU

McParlan said: "This case is not about Chrome. It is about ensuring free and fair competition on Windows PCs. We believe that, with its Windows OS, Microsoft is clearly dominant and that it is using that commercial power to award an unfair advantage to Edge.

"We think that, unless Microsoft is made to change its ways, Edge's share will continue to increase for reasons disconnected from product quality and user preferences."

Brazil isn't the only place where Opera has been airing its grievances. In July 2024, the company [11]filed an appeal requesting that the EU General Court annul the European Commission's decision not to designate Microsoft Edge as a gatekeeper under the Digital Markets Act (DMA). Should the appeal succeed, Microsoft would be required to display a browser choice screen on every Windows device.

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Perhaps ominously for Google and Apple, McParlan added: "Mobile and other platforms raise separate issues that may call for different solutions."

We asked Microsoft to comment on Opera's complaint, but haven't heard back. McParlan said: "Opera prefers not to comment on such elements of an ongoing case," when asked if the Windows giant had responded to the complaint.

While Opera has filed the complaint in Brazil, the allegations concern Microsoft practices around the world. This writer recently had to configure a new Surface device and was struck by the sheer volume of nagging and pleading within the operating system to stick with Edge rather than opt for an alternative. ®

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[1] https://support.microsoft.com/en-gb/windows/windows-10-and-windows-11-in-s-mode-faq-851057d6-1ee9-b9e5-c30b-93baebeebc85

[2] https://gs.statcounter.com/browser-market-share/desktop/brazil

[3] https://www.theregister.com/2010/02/19/microsoft_browser_screen/

[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aIpBiBQsUo37S8glt1tOhQAAANM&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0

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[7] https://www.theregister.com/2025/07/29/10_years_of_windows_10/

[8] https://www.theregister.com/2025/07/28/microsoft_edge_copilot_mode/

[9] https://www.theregister.com/2025/07/08/browser_hijacking_campaign/

[10] https://www.theregister.com/2025/06/03/microsoft_stops_eu_edge_pestering/

[11] https://blogs.opera.com/news/2024/07/opera-dma-request/

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[13] https://whitepapers.theregister.com/