Opera Files Antitrust Complaint Against Microsoft in Brazil Over Edge Browser Tactics

Norwegian browser firm Opera has filed an antitrust complaint against U.S. technology giant Microsoft with Brazil’s Administrative Council for Economic Defense (CADE) on July 29, 2025 (via The Verge). Opera’s petition alleges Microsoft’s methods for pre-installing and promoting its Edge browser on Windows devices violate fair competition, hinder user choice, and disadvantage rival browsers not only in Brazil, but globally.

This legal action reignites a decades-old browser war with new relevance as tech monopolies come under increasing scrutiny. For Microsoft, the complaint presents not just a regulatory challenge in one of its largest emerging markets, but a threat of renewed action from antitrust authorities worldwide.

Details of Opera’s Antitrust Complaint

Opera’s filing targets several Microsoft business practices:

• Pre-Installation and Default Status: Microsoft’s Edge comes pre-installed and set as the default browser on all Windows PCs. Opera alleges this practice blocks competitors from gaining equal footing when users first set up their computers and disproportionately impacts market share.

• Barriers to Competition: Claims Microsoft creates institutional barriers to alternative browsers. For example, links clicked in built-in apps like Outlook, Teams, Windows Search, or widgets automatically open in Edge—regardless of a user’s chosen default browser.

• “Dark Patterns” and Manipulative Tactics: Accuses Microsoft of using intrusive pop-ups and “manipulative design tactics” that steer users away from downloading rival browsers—precisely at the moment they search for an alternative.

• OEM Incentives: The complaint highlights “special incentives” allegedly offered to PC manufacturers to pre-install Edge and restrict OEMs from giving users real browser choices. Says Microsoft requires OEMs to “offer S mode devices as a prerequisite for rebates on a Windows OS license,” a move designed to limit browser selection.

• Global Implications, Local Filing: Although Opera’s grievances are global, Brazil was chosen for the complaint due to its status as one of Opera’s largest markets. Opera ranks as the country’s third most popular browser, with millions of loyal users.

“Microsoft obstructs browser competition on Windows at every opportunity. Initially, browsers like Opera are excluded from significant pre-installation chances. Furthermore, Microsoft complicates users’ efforts to download and utilize alternative browsers.”
— Aaron McParlan, General Counsel, Opera

The Regulatory Backdrop: What’s at Stake?

Microsoft is no stranger to antitrust controversies over browsers. In 2007, Opera instigated a landmark European Union case, leading to the implementation of the browser “ballot screen” and a €561 million fine for Microsoft in 2013 after the company failed to present users with a choice of browsers. The current complaint signals the Norwegian company’s belief that history is repeating itself—this time, under Microsoft’s Edge brand with new, software-driven obstacles.

CADE, Brazil’s powerful antitrust watchdog, is expected to thoroughly investigate whether Microsoft’s tactics breach fair competition rules in the booming tech sector. A ruling against Microsoft could force it to change its practices in Brazil and inspire similar actions in other jurisdictions.

Opera’s Demands

The Norwegian company’s remedy requests include:

• Requiring Microsoft to allow PC makers to preload alternative default browsers.

• Prohibiting Microsoft from blocking or deterring the installation of other browsers.

• Eliminating deceptive or manipulative banners and pop-ups that push users to stay with Edge.

• Stopping rebates or conditions to OEMs that disadvantage competitor browsers2.

Microsoft’s Response and Broader Fallout

Microsoft has yet to issue an official response to the complaint in Brazil. However, Microsoft has publicly defended its product integration in previous antitrust challenges—arguing these features benefit users and improve security.

If Opera succeeds, CADE could force sweeping changes in how Windows handles browser choice. Such a move would ripple outward, potentially influencing policy in Europe, North America, and beyond, as regulators scrutinize whether major platform owners unfairly leverage their operating system dominance.

The company’s initiative dovetails with growing international momentum toward curbing tech giants’ gatekeeping. Just last year, the company challenged the EU’s decision not to designate Edge as a “gatekeeper” service under the Digital Markets Act—an appeal still pending in European courts.

If regulators uphold the Norwegian company’s claims, Windows users in Brazil (and potentially elsewhere) may gain more transparent browser choices, sparking renewed competition and innovation in the browser space. Similar cases could be brought in other large markets, transforming the entire way users encounter browsers on new PCs.

Opera’s antitrust complaint against Microsoft in Brazil is far more than a regional spat—it is a high-stakes test of whether regulators can enforce genuine user choice in the face of entrenched platform power. The broader outcome could set precedents for tech regulation worldwide, ensuring fair competition for browsers and a less monopolized digital future.