What value disables seasonal skins?

Add ?AllowSeasonalSkins=0 to the server launch command. Use ?AllowSeasonalSkins=1 to enable them.

Where do I put the parameter?

In the map launch line of your KF2Server.bat, after the map name and other ? options.

KF2 Server: Enable or Disable Seasonal Skins (AllowSeasonalSkins)

Killing Floor 2 seasonal events add alternate looks for Zeds and characters. If you run a dedicated server and want those skins switched on or off for everyone, a single URL-style option does it. This is a short community tip.

The parameter

In your KF2Server.bat add one of these options to the launch line:

?AllowSeasonalSkins=0 - disables seasonal skins on the server.
?AllowSeasonalSkins=1 - enables seasonal skins on the server.

Example

start .\Binaries\win64\kfserver kf-dystopia2029?-AdminPassword=123?AllowSeasonalSkins=0

This starts the map kf-dystopia2029 with an admin password and seasonal skins disabled. Replace the map and password with your own, and keep all options joined with ? as in the example.

Notes

Set the option every time you launch the server; it is part of the startup string.
Restart the server after editing the batch file.
For more setup help see dedicated server and the list of seasonal Zeds in event Zeds and seasonal skins.

FAQ

What value disables seasonal skins?: Add ?AllowSeasonalSkins=0 to the server launch command. Use ?AllowSeasonalSkins=1 to enable them.
Where do I put the parameter?: In the map launch line of your KF2Server.bat, after the map name and other ? options.