Opera files antitrust complaint against Microsoft in Brazil, alleging unfair browser restrictions on Windows

Opera has submitted a formal complaint to Brazil’s Administrative Council for Economic Defense (CADE) alleging that Microsoft’s practices unfairly restrict browser choice on Windows devices.

The Norwegian company argues that Microsoft’s dominance in the operating system market allows it to give an artificial edge to its Edge browser, at the expense of competitors, such as Opera (naturally), and Brazilian users.

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Opera’s complaint was filed on July 29, 2025, as part of its broader international push for fair competition in the browser market.

The company believes Microsoft’s integration of Edge as the pre-installed and default browser on Windows PCs limits user freedom and weakens competition.

“Microsoft thwarts browser competition on Windows at every turn,” said Aaron McParlan, General Counsel at Opera. “First, browsers like Opera are locked out of important preinstallation opportunities. And then Microsoft frustrates users’ ability to download and use alternative browsers. If a person in Brazil wants to use a browser other than Edge on their Windows machine, they should be allowed to freely do so – without being actively obstructed or discouraged.”

According to Opera, Microsoft uses several design strategies that steer users toward Edge, even when they attempt to download or set another browser as default.

These include intrusive banners, messages that discourage downloading alternatives, and the overriding of user preferences in key areas, such as opening links in emails or PDFs.

The complaint highlights what Opera calls “manipulative design” patterns that make it harder for users to switch browsers or maintain their preferred settings.

Opera argues that these tactics harm both user experience and the competitive landscape by discouraging the adoption of alternatives based on their own merits.

McParlan said the issue extends beyond Brazil and is a global concern. “The fight for digital freedom is global, and we are taking this step on behalf of the many millions of Brazilian users who are being denied genuine choice,” he said. “Brazilians are very engaged and enthusiastic users of consumer tech products and they deserve fair access to the browser that best suits their needs. Microsoft’s manipulative tactics on Windows PCs are a disservice to Brazilian consumers and stifle innovation as well as competition on the merits.”

Opera’s request

Opera is requesting that CADE investigate Microsoft’s practices and consider remedies such as allowing PC manufacturers to preload and set rival browsers as default, requiring a neutral browser choice screen during setup, and banning design behaviors that limit consumer choice.

While this is a Brazil filing, it is part of Opera’s wider global push for fair browser competition, echoing the past legal action it took against Microsoft in Europe, where it argued that Edge qualifies as a gatekeeper service under the law’s thresholds.

The company believes that a level playing field will not only support consumer freedom, but also foster browser innovation across the industry.

What do you think about Opera’s latest filing against Microsoft? Let us know in the comments.

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