In a move that echoes longstanding tensions in the tech industry, Norway-based Opera Software has lodged a formal antitrust complaint against Microsoft with Brazil’s Administrative Council for Economic Defense (CADE), accusing the tech giant of employing anti-competitive tactics to bolster its Edge browser at the expense of rivals. According to details reported by Reuters, Opera alleges that Microsoft provides incentives to major PC manufacturers to pre-install Edge exclusively on Windows devices, effectively locking out competitors like Opera from fair market access. This complaint, filed on Tuesday, highlights what Opera describes as manipulative design elements within Windows that steer users toward Edge, such as persistent prompts and default settings that are difficult to change.

Opera’s grievances extend beyond pre-installation deals, pointing to broader strategies that hinder browser choice. The company claims Microsoft uses “dark patterns” in its operating system—subtle user interface tricks that make it cumbersome for users to switch to alternative browsers. Posts on X, formerly Twitter, from tech journalists like Tom Warren of The Verge underscore this sentiment, noting Opera’s frustration with Microsoft’s preferential treatment of Edge, which reportedly includes tactics that override user preferences during updates or searches.

Historical Echoes of Browser Wars

These accusations are not isolated; they revive memories of Microsoft’s past antitrust battles, particularly the infamous U.S. case in the late 1990s involving Internet Explorer. As detailed in a 2021 article from Windows Central, Vivaldi’s CEO Jon von Tetzchner has long criticized similar promotional tactics for Edge as “desperate” and reminiscent of Microsoft’s earlier dominance. Opera’s current filing builds on this narrative, arguing that despite regulatory scrutiny in regions like the European Union, Microsoft continues to leverage Windows’ ubiquity—installed on over a billion devices—to favor its own browser.

Recent data from sources like The Register shows Edge’s market share grew modestly in 2024, but not dramatically, hovering around 5% globally compared to Chrome’s dominance at over 65%. Yet Opera, which claims to be the third-most popular PC browser in Brazil with features like built-in VPN and ad-blocking, argues that Microsoft’s practices stifle innovation and competition, preventing browsers like its own from gaining traction.

Allegations of Incentives and Design Manipulation

Delving deeper, Opera’s complaint specifies that Microsoft offers financial incentives or technical support to OEMs (original equipment manufacturers) for exclusive Edge pre-installation, a practice that allegedly violates antitrust principles by creating barriers to entry. This is corroborated by reports from gHacks Tech News, which noted the formation of the Browser Choice Alliance in late 2024, including Opera, Chrome, Vivaldi, and others, to collectively challenge Microsoft’s Edge favoritism. The alliance has pushed for regulatory intervention, emphasizing how Windows’ integration gives Edge an unfair edge in areas like search and AI features.

Moreover, Opera points to user experience hurdles, such as pop-ups that discourage downloading rival browsers or settings that reset to Edge after system updates. A 2025 comparison by MSPoweruser highlights Opera’s strengths in privacy and performance, yet notes how Microsoft’s ecosystem lock-in diminishes these advantages. Industry insiders suggest this could prompt CADE to investigate, potentially leading to fines or mandated changes, similar to EU actions under the Digital Markets Act.

Broader Implications for Tech Regulation

The timing of Opera’s complaint aligns with global scrutiny of Big Tech’s market power. In Europe, as reported by Seeking Alpha in October 2024, Opera joined other developers in complaining to the European Commission about Edge’s advantages, arguing it undermines the DMA’s goal of fair competition. X posts from figures like Open Web Advocacy reflect ongoing sentiment that browsers from Microsoft, Google, and Apple form “walled gardens” that limit choice, with one thread from 2022 detailing how such practices erode user privacy and innovation.

Microsoft has not yet publicly responded to the Brazilian filing, but past statements from the company, as covered in PCMag‘s 2025 browser roundup, emphasize Edge’s security and integration benefits as user-focused rather than anti-competitive. However, critics argue this ignores the coercive elements.

Potential Outcomes and Industry Shifts

If CADE rules in Opera’s favor, it could force Microsoft to offer easier browser selection during Windows setup or cease exclusive deals with manufacturers, reshaping how browsers compete in emerging markets like Brazil. This echoes alliances like the one described in Winaero from 2021, where Vivaldi’s leader decried Edge’s promotion as anti-competitive.

For industry insiders, this case underscores the evolving battle for browser supremacy, where features like AI integration and privacy tools are secondary to platform control. As GeeksforGeeks noted in a 2025 analysis, while Edge excels in Windows synergy, Opera’s customizability appeals to power users—yet without level playing fields, true competition remains elusive. Regulators worldwide will watch closely, as a win for Opera could inspire similar challenges elsewhere, potentially curbing Microsoft’s influence in the browser arena.