I'm running Windows 11 with Bitdefender Antivirus and Mullvad VPN on a 1 Gbps fiber connection. For several weeks, Chrome, Edge, and Firefox have all taken around 10–15 seconds to load sites such as Gmail and Microsoft's Edge page. Other devices on the same network work normally, and changing my DNS server didn't help. The strange part is that enabling Mullvad makes everything load almost instantly—Gmail takes about a second. What could cause this, and what diagnostics can I run to compare the connection with and without the VPN? I'm also wondering whether malware could be involved.
2 Answers
I’m seeing something very similar: several browsers become unusable while other applications, Discord, and even non-browser speed tests keep working. That points toward a browser-wide component such as an antivirus HTTPS filter, proxy setting, network driver, or intermittent connection handling—not necessarily an infection. Check Windows proxy settings, browser extensions, and whether Bitdefender is installing a traffic-scanning certificate. You can also test from a clean browser profile or Windows Safe Mode with networking to narrow down whether third-party software is involved.
Since the VPN makes the browsers faster, this sounds more like a routing, filtering, or security-software issue than a lack of bandwidth. The VPN changes your route and may also avoid something on the normal connection path. Check Bitdefender’s web protection, encrypted-traffic scanning, firewall, and network-adapter settings. Temporarily disabling those protections one at a time can help identify a conflict, but turn them back on after testing. Also compare `tracert google.com` and `nslookup gmail.com` with Mullvad disconnected and connected. If only the non-VPN route is slow, the problem may be upstream from the PC rather than malware.
I checked Bitdefender and found that its separate VPN product had actually been uninstalled previously, so only the antivirus is installed. I’ll compare the traceroutes and test its web-filtering features individually.