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Npcap Users' Guide

Q & A

  • Network disconnects after installing Npcap: As Microsoft states here, an optional NDIS light-weight filter (LWF) driver like Npcap could cause 90-second delay in network availability. Some solutions you could try are: 1) wait for 90 seconds; 2) disable and re-enable the adapter icon in ncpa.cpl; 3) reboot. If this doesn't work, please file a bug report.

  • Installation fails with error code 0x8004a029: The cause is that you have reached the maximum number of network filter drivers, see solution here.

  • Npcap Loopback Adapter is missing: Npcap Loopback Adapter is actually a wrapper of Microsoft Loopback Adapter. Such adapters won't show up in Wireshark if the Basic Filtering Enging (BFE) service was not running. To fix this issue, you should start this service at services.msc manually and restart the Npcap service by running net stop npcap and net start npcap. See details about this issue here.

  • Npcap only captures TCP handshake and teardown, but not data packets. Some network adapters support offloading of tasks to free up CPU time for performance reasons. When this happens, Npcap may not receive all of the packets, or may receive them in a different form than is actually sent on the wire. To avoid this issue, you may disable TCP Chimney, IP Checksum Offloading, and Large Send Offloading in the network adapter properites on Windows. See details about this issue in issue #989 on our tracker.

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