Opera Takes on Microsoft in Brazil: Antitrust Complaint Slams Edge for Unfair Dominance

Opera has officially filed an antitrust complaint against Microsoft in Brazil, submitting it on July 29, 2025 to the Brazilian competition authority, CADE. The complaint alleges that Microsoft unfairly leverages its Windows operating system to give its Edge browser uninterrupted advantage over rivals. The core accusation is that Microsoft pre-installs Edge as the default browser across all Windows devices, unfairly limiting the visibility and market access for competing browsers such as Opera.

Opera argues that Microsoft goes beyond mere pre-installation by actively discouraging users from switching away from Edge. The complaint details a range of interface tactics—commonly known as “dark patterns”—such as intrusive pop-ups and banners that deter users from downloading alternative browsers. It also claims that even when users set a different default browser, Windows frequently overrides this preference in contexts like opening links from emails, PDFs, widgets, or the search bar.

Further concerns center around Microsoft’s OEM relationships. Opera alleges that PC manufacturers are offered exclusive financial incentives to pre-install Edge—a condition tied specifically to devices shipped in Windows “S mode,” which restricts the installation of non-Microsoft browsers. Users may be effectively blocked from switching out of S mode due to these industry-wide arrangements.

Opera emphasizes that this complaint goes beyond a commercial dispute; it’s about consumer choice. Citing its own browser’s 6.78 percent share of Brazil’s desktop market—compared to Edge’s 11.52 percent and Chrome’s nearly 75 percent—the company portrays Brazil as a critical battleground. It suggests that the country’s engaged user base and active tech ecosystem make it a fitting jurisdiction to challenge Microsoft’s global practices.

In response, Opera calls on CADE to enforce meaningful remedies. These include requiring device makers to be allowed to pre-install and set alternative browsers as defaults, banning interface tactics that steer users toward Edge, and implementing a neutral, unbiased browser choice screen that lets users select among popular browsers during setup.

Opera’s history of legal actions targeting Microsoft underscores that this is not a new fight. The company previously filed a complaint with the European Commission in 2007 over bundled Internet Explorer browser access, a case that led to a €561 million fine and the eventual introduction of a browser choice ballot screen in Windows. More recently, Opera challenged the European Commission’s decision not to classify Edge as a “gatekeeper” under the Digital Markets Act—an effort that continues as appeals.

Microsoft has not yet issued a public comment on the filing. If CADE determines that Microsoft’s practices violate Brazilian competition law, the outcome could compel changes in Windows distribution and OEM policies across Latin America. The case may also rekindle global debate over how platform owners can favor their own software and how regulators should protect consumer choice in digital markets—a controversy that Opera’s continued advocacy seeks to challenge far beyond Brazil’s borders.

Thank you for reading this post, don't forget to subscribe & share!