Every single firewall that supports Windows Vista and later is probably built upon WFP. TDI, which was the way to intercept applications accessing the network before, has been deprecated for over a decade now and doesn't allow to regulate Windows apps. So everyone switched ages ago. In theory, multiple WFP drivers are fully compatible with each other as Microsoft takes care of properly layering drivers on top of each other. So there aren't any issues, in theory at least. The much bigger issue is to find a firewall that is just a firewall. It is much more likely that our behaviour blocker conflicts with the sandbox/HIPS style parts of most firewalls that aren't just a reskin of the Windows Firewall interfaces. That being said, the only firewall we officially support and do any compatibility testing with is the Windows Firewall. So that is our recommendation and clearly mentioned in the blog post. Third-party applications that sit on top of the Windows Firewall are probably okay as well, like Windows Firewall Control, Windows Firewall Notifier, TinyWall and GlassWire.