The Browser Choice Alliance fired a shot across Microsoft’s bow this week, and it is about time. A coalition of browser developers (Vivaldi, Brave, Waterfox, and several smaller forks) has filed a formal complaint with the European Commission (the executive branch of the EU that enforces competition law) over the way Edge is bundled into Windows 11, and the complaint is short, specific, and aimed at the part of the Windows 11 setup that most users never see. The complaint is not about defaults, and it is not about the Bing button in the Edge toolbar. It is about the moment in the Windows setup flow where Edge silently gets pinned to the taskbar and the file associations for HTML, PDF, and SVG are claimed before the user has clicked anything. That moment is the one the Browser Choice Alliance is calling anticompetitive, and the complaint has teeth because of the same Digital Markets Act (the 2022 EU regulation that forces “gatekeeper” platforms like Windows to interoperate with third-party services) that forced Microsoft to ship the search-box toggle I wrote about last week. The Windows team has been walking back the visible Bing integrations for a year, but the file-association race in the setup flow is the part they have not touched, and the Browser Choice Alliance is asking the Commission to make them.
What the complaint actually says
The complaint is 14 pages and it focuses on a single technical detail: the order in which Windows 11 setup runs the “associate your file types” step. During the out-of-box experience (the first-run flow that walks a new user through naming their PC, signing into a Microsoft account, and choosing privacy settings), Windows 11 claims the default browser for HTML, HTTPS, PDF, and SVG file types before the user has had a chance to pick a browser themselves. The “Choose your default browser” screen does show up later in the flow, but by then the file associations are already set to Edge, and the dialog that lets the user pick a different browser is a single checkbox buried in a list of nine other default-app categories.
Browser developers Vivaldi, Brave, and Waterfox have a different read on the situation. Their argument is that the order of the steps in the setup flow is not accidental, and the file-association race is the entire reason the “Choose your default browser” screen is positioned where it is. The complaint’s framing is that consent obtained through a setup flow the user did not design is not real consent, and the Commission has been receptive to that framing in past cases.
The third-party browser angle is the part that gives the complaint momentum. Vivaldi, Brave, and Waterfox are not the only browser vendors affected, but they are the ones that joined the complaint. All three have business models that depend on the user picking a non-Edge browser, and all three have spent the last three years filing individual complaints with the Commission that have not gone anywhere. The Alliance is a coordinated filing, and the Commission is more likely to open a formal investigation when the complaint comes from a coalition than when it comes from a single vendor.
Why the file-association race matters
If you have ever installed a second browser on Windows 11 and watched Edge keep the file associations anyway, you have hit the race the complaint describes. The behavior is that when you install a new browser and check the “Always use this app” box, the new browser gets the file association for the file type you opened, but Windows 11 quietly keeps the association for every other file type that Edge claimed during setup. There is no warning that this is happening. There is no “Edge is also your default for these other file types” notification. The user has to open the Default Apps settings panel and uncheck each file type by hand.
For a user who only opens a few file types a week (HTML and PDF being the obvious two), the race is invisible. The default browser works, the file types open, and the user has no reason to think anything is wrong. For a user who has installed Vivaldi or Brave or Firefox specifically to get away from Edge, the race is the reason their default-browser pick only works for some file types. The third-party browser is the default for the file type they tested, but Edge is still the default for SVG, XHTML, FTP, MAILTO, NEWS, and half a dozen other protocols that the user did not think to test.
The fix Microsoft could ship tomorrow is to change the setup flow to (1) show the default-browser screen first, (2) wait for the user to pick a browser, and (3) apply the file associations based on the pick. The current flow does the opposite: claim file associations, then ask the user to pick a browser, then apply the pick to the file types the user explicitly mentions. The complaint is asking the Commission to compel the first ordering. The technical change is small. The political change (admitting the current order is a competitive choice, not a technical necessity) is the hard part.
What Microsoft is likely to argue
Microsoft will probably argue three things in response to the complaint. First, that the file-association race is a technical requirement, not a competitive choice, because Windows 11 needs to know which app handles HTML and PDF before the setup flow can render the consent dialogs that depend on the browser. This is a weak argument because the consent dialogs in question are HTML-based but render fine in whatever browser is associated with the file type at the moment the dialog opens. Microsoft could change the order without changing the dialogs.
Second, Microsoft will probably argue that the user can change the defaults at any time, and the Browser Choice Alliance is overstating the harm because the change is one Settings panel away. This is the stronger argument, but it ignores the empirical pattern that most users do not change defaults they did not set. The setup flow that claims the file associations is the moment when 80 percent of Windows users make their default-browser decision, and the decision is “Edge, because that is what the box says.” The complaint’s counter-argument is that consent obtained through a setup flow the user did not design is not real consent, and the Commission has been receptive to that framing in past cases.
Third, Microsoft will probably argue that the Edge integration in Windows 11 is required for the Copilot features that ship in the OS. This is the weakest argument because Copilot works fine in any browser, and the parts of Copilot that are Edge-specific (the “ask Copilot about this PDF” right-click menu) are the parts the complaint is specifically about. Microsoft conflating the OS-level Copilot with the browser-level Copilot is the rhetorical move that the Browser Choice Alliance will press hardest on.
What changes if the Commission opens a formal investigation
The Commission has 25 working days to decide whether to open a formal investigation after a complaint is filed. The 25-day clock started on June 9, 2026, which means a decision is due by July 14, 2026. The Commission’s pattern in DMA cases is to open a formal investigation when the complaint is specific enough to act on, and the Browser Choice Alliance’s complaint is unusually specific. The 14-page document names the exact step in the setup flow, the exact file types affected, and the exact ordering that the Alliance wants changed. That level of detail is the kind of thing the Commission staff look for when deciding whether to open a case.
If the Commission opens a formal investigation, Microsoft will have a chance to respond and propose a remedy. The remedy Microsoft is most likely to propose is a tweak to the setup flow that adds an extra “confirm your default browser” step but does not change the file-association order. That kind of remedy has worked in past cases (the 2009 IE settlement was a similar tweak), and the Commission has been willing to accept it when the complainant is satisfied. The Browser Choice Alliance has signaled in the complaint that a tweaked setup flow is acceptable, which gives Microsoft room to propose a remedy that satisfies both sides.
If the Commission rejects the remedy, the case moves to a formal ruling, and the ruling can include fines of up to 10 percent of Microsoft’s global annual revenue. The 10 percent figure is a ceiling, not a starting point, and the actual fine in past DMA cases has been closer to 1-2 percent. For Microsoft, 1 percent of global revenue is around $2.5 billion, and 2 percent is around $5 billion. Those numbers are large enough to get the Windows team’s attention, but small enough that Microsoft can absorb them as a cost of doing business. The bigger cost is the precedent: if the Commission rules against Microsoft on the file-association race, every other “gatekeeper” platform (Apple’s iOS, Google’s Android, Amazon’s marketplace) is next.
The user’s path forward
For a user who is on Windows 11 today and wants to make sure their default browser actually wins the file-association race, the fix is the one that has been there for a decade. Open Settings, Apps, Default apps, and click on the browser you want. Then scroll through the file types one by one and confirm the browser is set. The list is long (HTML, HTTPS, HTTP, FTP, MAILTO, NEWS, SVG, XHTML, PDF, and a handful of others), and the defaults for file types you did not click will revert to Edge the next time Windows does a major feature update.
The fix is annoying, and it is the reason the Browser Choice Alliance’s complaint has a sympathetic audience among Windows power users. The setup flow could be doing the right thing automatically. The reason it is not doing the right thing automatically is the reason the complaint exists. If the Commission opens a formal investigation and Microsoft is forced to flip the order, the fix becomes invisible. The user picks a browser in the setup flow and the file associations follow. That is what the Browser Choice Alliance is asking for, and it is the change Microsoft has had twelve years to make on its own.
For users on macOS or Linux, the complaint is a useful reminder that the file-association race is a Windows-specific problem, and the equivalents on other platforms are not as severe. macOS asks the user to confirm the default browser the first time they open a link in a non-Safari browser, and the file associations for HTML, HTTPS, and PDF follow the browser pick. Linux desktops vary, but the major ones (GNOME, KDE, XFCE) have a similar pattern. The Windows case is the outlier, and the complaint is asking the Commission to bring Windows in line with the rest of the industry.
Trade-offs
The Browser Choice Alliance’s complaint is not free to bring. The four founding members (Vivaldi, Brave, Waterfox, and one smaller fork) are spending legal fees on a case that may or may not produce a remedy. The complaint took eight months to draft, and the lawyers involved are the same ones who worked on the original 2009 IE case. The trade-off for the Alliance is that a successful complaint produces a setup-flow change that benefits every non-Edge browser, including the ones that did not join the complaint. The free-rider problem is real, and the Alliance’s decision to file as a coalition rather than as individual vendors is the response.
Microsoft faces a different set of trade-offs. Flipping the setup flow is a small technical change but a large strategic concession. The file-association race is the last visible Edge advantage on Windows, and giving it up means that the next time a user installs a third-party browser, the third-party browser will actually win all the file types by default. The strategic value of that win to Vivaldi, Brave, and Waterfox is large (it materially improves their conversion rate from “installed once” to “used daily”), and the strategic cost to Microsoft is the loss of the last remaining Edge bundling lever.
Users are the third party in the trade-off matrix. Power users who already know to set the defaults will not see a change. Casual users who never changed a default in their life will see a one-time setup flow that asks them to pick a browser, and the majority of them will pick Edge anyway (because that is what the box says, and the prompt does not differentiate between “I want Edge” and “I have not thought about this”). The complaint’s predicted outcome is that the third-party browser conversion rate goes up by 5-10 percent in the first six months after the fix, and Edge’s share of new installs on Windows drops by a corresponding amount. The numbers are small, but the precedent is large.
If you are a Windows user and you care about which browser handles your file types, the fix is the one you have always had: open the Default Apps settings and click through the file types. The complaint is a structural fix that benefits future Windows users, not a fix for the setup you already ran. If you are a Vivaldi, Brave, or Waterfox user, the complaint is a sign that the browser wars in 2026 are not about features, they are about defaults, and the defaults are decided in the setup flow that 80 percent of users never customize. If you are a Microsoft shareholder, the complaint is a sign that the regulatory pressure that started with the 2009 IE case has not gone away, and the next four years of Windows setup flows are going to be a series of small concessions to the Commission.
What I would tell past me
Three things, if I could send them back.
- The file-association race in Windows 11 setup is the single most important thing the Browser Choice Alliance is fighting. The complaint is 14 pages long, but the core argument is one paragraph: claim the file associations first, ask the user to pick a browser second. The Commission has been receptive to that framing in the past, and the Alliance is betting the same framing works here.
- Microsoft has had twelve years to flip the order. The 2009 IE settlement required Microsoft to show a “Choose your default browser” screen, and the order of that screen relative to the rest of the setup flow was a deliberate choice. The fact that the order has not changed in twelve years is the strongest evidence the Alliance has, and it is the part of the case the Commission staff will look at first.
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The 25-day clock is the one to watch. The Commission is due to decide by July 14, 2026, whether to open a formal investigation. If the Commission opens the case, the Windows team has six months to propose a remedy. If the case closes without action, the Browser Choice Alliance has to decide whether to file again in 2027 with a different argument, and the file-association race continues. The 25-day clock is the part that turns the complaint from a press release into a real legal proceeding. If you want to know whether the case is going to gain traction, the four signals worth watching are:
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The Commission opens a formal investigation on schedule (the staff have 25 working days from June 9, 2026). A decision by July 14, 2026 to open the case means the Commission agrees the complaint is specific enough to act on. A decision to take more time (the “we need additional information” move) is a delay tactic, not a dismissal.
- Microsoft proposes a remedy in the first 30 days after the case opens. A fast remedy proposal is a sign the Windows team wants to settle before the case reaches a formal ruling. A slow proposal (or no proposal at all) is a sign the case is going to a hearing.
- The Browser Choice Alliance expands its membership. If Mozilla or Google or Apple joins the complaint, the coalition gets harder to dismiss. The current four-member coalition is specific but small, and the addition of any major browser vendor changes the political weight.
- The Commission’s DMA enforcement team makes a public statement about the file-association race. The DMA team has been quiet on Windows setup flows since the 2024 Edge antitrust ruling, and a public statement is the strongest signal that the Commission is treating this complaint as part of a broader pattern.