@Nils-Sjoberg thats work normally. I always use it for release windeployqt.exe C:\Users\B\Desktop\Projects\MyApp\build\MyApp\ worked : (windeployqt6.exe C:\Users\B\Desktop\Projects\MyApp\build\MyApp\MyApp.exe) What is the different windeployqt.exe and windeployqt6.exe ? also windeployqt.exe --webenginecore C:\Users\B\Desktop\Projects\MyApp\build\MyApp\ //or windeployqt.exe --webenginewidgets C:\Users\B\Desktop\Projects\MyApp\build\MyApp\ working

@MonkeyBusiness If you use normal resources (not external resources) then there is no need for this because the resources will be part of the executable file. You also did not answer any of the latest questions...

Okay, after four days of research, turns out the specific DLL - Qt5WebEngineCore.dll doesn't like being compressed by UPX. It's not noticeable immediately, but on approx. 10 % of PCs the QtWebEngineProcess simply crashes.