For about a week, downloads and uploads have become extremely slow on my Windows 11 PC, but only when using web browsers. I work with large video files, so I'm familiar with my usual speeds: uploading a 10 GB file recently took around 24 hours, while browser downloads fluctuate between 20 and 150 KB/s. Browser speed tests report roughly 3.5 MB/s download and 5.90 MB/s upload, which doesn't match real file transfers.
The same internet connection works normally on my phone, another Windows laptop, and in game clients such as Steam and Riot. Online gaming is also fine, but streaming YouTube in a browser is slow. Some sites, including Gmail and Google Docs, load slowly while others work normally. The problem happens over Ethernet, my usual Wi-Fi, and a different Wi-Fi network, so it appears to be specific to browser traffic on this PC.
I've already tried changing browsers, restarting the PC and router, switching networks and Ethernet ports, changing DNS servers, scanning for malware, disabling VPNs and browser extensions, updating drivers and Windows, resetting Winsock and TCP/IP, renewing the IP address, flushing DNS, resetting network settings, changing Ethernet duplex settings, disabling Large Send Offload, and disabling unnecessary startup apps. I haven't changed my internet plan or physically modified the PC. One secondary hard drive also occasionally clicks, although I'm not sure whether that is related. What else could cause browsers to be slow while other applications remain normal?
2 Answers
The clicking hard drive is worth checking separately, especially if it contains important files, but it probably isn’t responsible for slow browser traffic if the operating system and browsers are running from another drive. Back up anything important and check the drive’s health. For the network problem, compare browser performance in a clean boot or Windows Safe Mode with Networking; if speeds return there, re-enable services one at a time to identify the filter or utility causing the slowdown.
Since other devices, game clients, and different connection types work normally, this is probably not an ISP or router problem. The useful next step is to check the PC’s network adapter properties for third-party filter software or traffic-inspection components. Security suites, VPN remnants, parental-control tools, and other network utilities can affect browser traffic even after their browser extensions or visible apps are disabled. Checking the full adapter properties and temporarily disabling non-Microsoft filters can help isolate the cause.
That turned out to be the issue. I found an advanced Ethernet setting that disabled third-party software or filters for browser traffic. Disabling it restored my normal upload and download speeds, although I couldn’t find the exact setting again afterward.