Yes, a Windows 11 update killed "localhost" support — Microsoft breaks Windows again
Windows 11’s latest update breaks a core developer feature, forcing users to uninstall security patches.

On October 14, 2025, Microsoft released the Windows 11 cumulative update KB5066835. It was intended to deliver security fixes and stability improvements, but instead introduced a serious problem. The update broke localhost functionality for many users, causing major disruption for developers who rely on local testing every day.
Reported on by TechPowerUp, the update broke localhost connections, which use the 127.0.0.1 or localhost address and are essential for testing websites, apps, and APIs on a local machine. After the update, browsers could no longer load anything running on localhost, and local projects stopped responding entirely.
Localhost is a loopback network address that essentially allows a PC to communicate with itself. It is used by developers to run and test websites or applications locally before pushing them online. It also powers common development tools like Visual Studio, MySQL, PostgreSQL servers, and Docker.
This does not affect everyday users who only browse the web or use normal apps. It is a serious problem for developers, though, because localhost is central to coding, debugging, and testing work.
The root cause has been traced to HTTP.sys, a low-level Windows networking component that handles HTTP and HTTPS connections behind the scenes. The update changed how HTTP.sys processes loopback traffic, which caused local connections to fail or reset.
Microsoft has confirmed the issue and has deployed a fix. However, the community did find a workaround to resolve the issue before Microsoft pushed a patch. Uninstalling the KB5066835 update restores localhost functionality. Some users also had to remove the September preview update KB5065789 if both updates were installed. It’s also worth noting that some users are still reporting the issue.
There is a trade-off. Removing the update also removes recent security patches, so users need to decide whether to wait for an official fix or uninstall the update to continue working.
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Another Windows update headache, and a familiar pattern is forming
Windows updates breaking things is not a rare occurrence, and localhost failing is not an isolated incident. Updates have been causing noticeable issues recently, especially for power users, developers, and IT admins. Maybe it is recency bias, and we are more aware of problems now that the perception of Microsoft is lower than ever. However, it does feel like Windows is breaking more often than it should.
Microsoft recently broke the Windows Recovery Environment, which made USB keyboards and mice unusable during system recovery. It had to push out an urgent fix to stop users from being locked out of their own systems.
Another update accidentally broke the Windows Media Creation Tool, which people rely on to install or repair Windows. That issue surfaced just a day before Windows 10 reached the end of its support.
With Windows 10 now officially discontinued as of October 14, 2025, Windows 11 is the only operating system Microsoft offers. The timing is not great. A growing number of users are already frustrated, and the recent spike in problems sets a worrying tone for the future of Windows.
Maybe it is a general sense of doom surrounding Microsoft lately, especially with criticism aimed at the direction of Windows and Xbox. Or maybe it is something else. Satya Nadella has said that 30 percent of Microsoft’s code is written with the help of AI. If true, I hope that code is still being reviewed by real engineers and not pushed straight into live builds without proper testing.
Microsoft needs to restore trust in Windows updates
This is part of a wider problem. Confidence in Windows updates is falling. More people than ever are seemingly delaying updates out of fear that something important will break, and that mentality goes directly against Microsoft’s own security advice. If people feel safer avoiding updates, something has gone wrong.
For developers, this is more than an inconvenience. Localhost is a core part of the workflow. It should never break from a standard security update. With Windows 10 now officially retired, Windows 11 cannot afford to feel unstable or unpredictable, especially when Microsoft wants developers to stay invested in the platform.
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Adam is a Psychology Master’s graduate passionate about gaming, community building, and digital engagement. A lifelong Xbox fan since 2001, he started with Halo: Combat Evolved and remains an avid achievement hunter. Over the years, he has engaged with several Discord communities, helping them get established and grow. Gaming has always been more than a hobby for Adam—it’s where he’s met many friends, taken on new challenges, and connected with communities that share his passion.
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