As keith already mentioned, this might not be possible to change! Same goes btw. for character sheets. If you open sheets inline, dark mode gets applied. However if you open them in a separate window, this is not the case... It is a known "feature" since darkmode was released for VTT. Dio G. said: Exactly what it says on the tin, Handouts you open in Dark Mode appear as if in Light Mode when opened to an external tab.