WinPcap is a free and open source packet sniffing library for Microsoft Windows operating systems. The library is compatible with libpcap but the implementation is necessarily tailored to the Microsoft device driver model.
WinPcap is no longer under active maintenance and has not been updated since 2015.
WinPCap is a great Windows based, open source driver for packet sniffing wire-based networks using a bog standard network interface card. WinPCap is licensed under the General Public License (GPL).
From a commercial software developers perspective, the GPL can be quite intimidating. Consequently, a lot of commercial developers won’t touch GPL’ed code with a very long barge pole.
Fortunately, the developers of WinPCap have come up with a commercial developer friendly version of WinPCap, WinPCap Professional.