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Opera Files Antitrust Complaint Against Microsoft in Brazil Over Browser Practices

By  |  July 30, 2025

Opera has lodged a formal antitrust complaint against Microsoft with Brazil’s Administrative Council for Economic Defense (CADE), accusing the tech giant of using its dominant position in the operating system market to give Microsoft Edge an unfair advantage in the browser sector.

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    According to a statement reported by GHacks, Opera alleges that Microsoft undermines fair browser competition by pre-installing Edge on all Windows-powered devices. The Norway-based software company claims this practice effectively excludes rival browsers from preinstallation opportunities, creating an unequal playing field from the outset.

    Opera’s complaint further criticizes Microsoft’s design choices, accusing the company of employing user interface tactics that discourage users from downloading and switching to alternative browsers. Per a statement, Opera believes these so-called “dark patterns” are aimed at retaining users within the Edge ecosystem, especially when they attempt to download competing browsers via Edge or the Bing search engine.

    The company also expressed concern over what it describes as persistent prompts and notifications within Windows 11 that push users to adopt Edge, even when a third-party browser has been selected as the default. Opera argues that such practices obstruct user autonomy and limit consumer choice.

    Related: Brazil Launches Antitrust Investigations into Big Tech AI Acquisitions

    Opera has urged CADE to launch an investigation into Microsoft’s conduct, stating that regulatory scrutiny is essential to preserve competitive balance in the browser market. If Microsoft is found to have violated Brazil’s antitrust regulations, it could face potential sanctions or be compelled to revise its integration strategies for Edge within Windows.

    This isn’t Opera’s first legal action against Microsoft in recent months. In June 2024, the company filed a lawsuit against the European Commission over its decision to exempt Microsoft Edge from the Digital Markets Act (DMA). That case remains ongoing. Opera, along with other members of the Browser Choice Alliance—including Chrome, Vivaldi, Waterfox, and Wavebox—has also advocated for Microsoft Edge to be designated as a gatekeeper under the DMA framework.

    Last month, Microsoft announced a series of changes in response to European regulatory scrutiny, including ending the practice of prompting users to set Edge as the default browser if it had not been actively used. However, Opera maintains that further action is needed globally to ensure equitable treatment for all browsers.

    Source: GHacks