Please report any bugs or issues about Npcap on
the Nmap Project's Issues tracker.
In your report, please provide your DiagReport output, user
software version (e.g. Nmap, Wireshark), steps to reproduce the problem, and other information
you think necessary. If your issue occurs only on a particular OS version (e.g. Win10
1511, 1607), please mention it in the report.
Npcap has provided a diagnostic utility called
It provides a lot of information including OS metadata, Npcap related files,
install options, registry values, services, etc. You can simply click the
C:\Program Files\Npcap\DiagReport.bat file to run
It will pop up a text report via Notepad (it's stored in:
Please always submit it to us if you encounter any issues.
For Vista users:
DiagReport is a script written for
and Vista doesn't have it installed by default. So if you are using Vista,
you need to install PowerShell 2.0 (KB968930) on your
system. Please download it here for x86
and here for x64.
Win7 and later systems have built-in PowerShell support and don't need
to do anything about it.
Npcap keeps track of the installation in a log file:
C:\Program Files\Npcap\install.log. Please submit it
together in your report if you encounter issues during the installation
(e.g. the installer halts).
Npcap keeps track of the driver installation (aka commands run by
NPFInstall.exe) in a log file:
C:\Program Files\Npcap\NPFInstall.log, please submit
it together in your report if you encounter issues during the driver
installation or problems with the “Npcap Loopback Adapter”.
There's another system-provided driver installation log in:
If you encounter errors during the driver/service installation, please copy
the Npcap-related lines out and send them together in
Dynamic link library (DLL) log
For problems with Npcap's regular operation, you may need to obtain a
debug log from
Packet.dll. To do this, you will
need a debug build of Npcap. If you are a Npcap developer, you can build
Packet.sln project with the
_DEBUG_TO_FILE macro defined. If you are an end user,
you can contact the Npcap development team for the latest Npcap debug
build. The debugging process will continue to append to the debug log
C:\Program Files\Npcap\Packet.log), so you may want
to delete it after an amount of time, or save your output to another
place before it gets too large.
If there is an issue with the Npcap driver, you can open an
Administrator command prompt, enter sc query
npcap to query the driver status and net start
npcap to start the driver (replace
<npf> if you
installed Npcap in “WinPcap Compatible Mode”). The command
output will inform you whether there's an error. If the driver is running
well, but the issue still exists, then you may need to check the driver's
log. Normal Npcap releases don't switch on the driver log function for
performance. Contact the Npcap development team to obtain a driver-debug
version of the Npcap installer. When you have got an appropriate
driver-debug version Npcap, you need to use DbgView
to read the Windows kernel log (which contains our driver log). You may
need to turn on DbgView before installing Npcap, if the error occurs when
the driver loads. When done, save the DbgView output to a file and submit
it in your report.
Blue screen of death (BSoD) dump
If you encountered BSoD when using Npcap, please attach the minidump
C:\Windows\Minidump\) to your report
together with the Npcap version. We may ask you to provide the full
C:\Windows\MEMORY.DMP) for further troubleshooting.