The Npcap installer and uninstaller are easy to use in
“Graphical Mode” (direct run) and “Silent Mode” (run with
The installer accepts several command-line options that correspond to the
options presented in the graphical interface (GUI). The options take the form
<name> is one of
The values for these options must be one of:
There is also one option that does not appear in the GUI, which is
/disable_restore_point=yes, which will prevent the
installer from setting a system restore point. Windows may independently
create a restore point because of the driver installation independent
from this option.
The destination directory for installation can also be overridden by
/D option, with a few restrictions. First, it will
only affect where Npcap keeps its installation logs and helper utilities.
The driver and DLLs will always be installed into the appropriate
directories below %SYSTEMROOT%\System32\. Second, the
/D must be the last option in the command, and the path
must not contain quotes. For example, to change the installation directory
C:\Path With Spaces\, the invocation would be:
<version>.exe /D=C:\Path With Spaces
An example of Npcap installer options is (for both “GUI Mode” and “Silent Mode”):
/npf_startup=yes /loopback_support=yes /dlt_null=no /admin_only=yes /dot11_support=yes /vlan_support=yes /winpcap_mode=yes
/npf_startup=yes: Automatically start the Npcap driver at boot time
/loopback_support=yes: Support loopback traffic (“Npcap Loopback Adapter” will be created)
DLT_EN10MB (Ethernet) as the
“Npcap Loopback Adapter”'s link layer protocol instead of the default
/admin_only=yes: Restrict Npcap driver's access to Administrators only
/dot11_support=yes: Support raw 802.11 traffic (and “Monitor Mode”) for wireless adapters
/vlan_support=yes: Support 802.1Q VLAN tag when capturing and sending data
/winpcap_mode=yes: Install Npcap in WinPcap API-compatible Mode
The uninstaller provided with Npcap also accepts some command-line options.
/Q flag means to skip the confirmation page and finish page in the uninstall wizard. So this option is
only meaningful for “GUI Mode”. The
/no_kill controls how the uninstaller handles
processes that are still using Npcap at the time of uninstall. If
is specified, then Npcap uninstaller will fail if there are still applications using Npcap driver or DLLs.
/no_kill=no is specified in silent mode, Npcap uninstaller will immediately terminate any command-line processes that are using
Npcap (like a Nmap process that is still scanning), and wait for at most 15 seconds to gracefully terminate any GUI processes
that are using Npcap (like Wireshark UI that is still capturing). “gracefully” means that if you are
still capturing via Wireshark, Wireshark UI will prompt the user about whether to save the current capture to a pcap.
So the user have 15 seconds to save his session. Note: although Npcap uninstaller won't terminate Wireshark UI processe
immediately, the live capture stops immediately. This is because Wireshark UI uses command-line processes named
dumpcap.exe to capture, and that command-line process will be terminated immediately. The default
no, but if the
graphical interface is used (without
/S), the user will be
prompted for what to do.
An example of Npcap uninstaller options is:
/S /Q /no_kill=yes
Disabled and enforced options for GUI Mode
We may disable or enforce certain options in the installer GUI to make them unselectable. This
usually means that those options can easily cause compatibility issues and are considered
not suitable for most users, or we think we need to enforce some rules for the Npcap API. Advanced users can still change their states via command-line
parameters, which is described in following sections.
Fortunately, if a distributor wants to start the Npcap installer GUI and disable or enforce
certain options for reasons like compatibility. It can also use the four value
mechanism by setting the command-line parameters to
For example, the following command will start an installer GUI with the
dlt_null disabled and unselected:
How to change options for GUI Mode
Default options for Npcap installer GUI can be changed. An example is:
<version>.exe /npf_startup=yes /loopback_support=yes /dlt_null=yes /admin_only=no /dot11_support=no /vlan_support=no /winpcap_mode=yes
Because most of these are the default values for these options, this example could be even simpler:
Running the installer
directly without options will see
Install Npcap in WinPcap API-compatible Mode
UNCHECKED by default in the “Installation Options” page.
However, the above two commands will launch the installer GUI, and in the “Installation Options” page, the
Install Npcap in WinPcap API-compatible Mode option will be CHECKED by default.
How to change options for Silent Mode
An example of changing option features for silent installation is:
<version>.exe /S /admin_only=yes /dot11_support=yes /vlan_support=yes
If you doesn't specify a parameter key, it will take the default value.
This is the same with the GUI.
The keys are case-insensitive.
The values are case-sensitive, only two values are