Mac green spot full screen

[Eboli]

All of a sudden (using OS 10.13.3) pressing the green dot in the top left corner of a window on my Mac no longer fills the whole computer screen (desirable, eg, when watching a film). Instead, it will only enlarge to the largest window inside the frame (leaving parts of the background visible). I've tried all the normal recommendations on-line (eg, Control with or without Shift when pressing green) and Fit to screen and float on top in the View menu and Zoom in Window menu. None of these resolves the issue, which just occurred (ie not after uploading an update). Any thoughts?

[madhatter]

Firstly I would consider updating to 10.13.4 though I doubt that would fix it by itself.

Secondly on a handful of occasions when I have encountered “something funny” I have fixed it by tossing out the appropriate preferences files and letting it build new ones.

Preferences files are in a Library folder which is normally hidden by default, though I set my Finder to show it.

You can still easily get to via the Finder Go menu, as you will see from macjack’s reply on this thread:
https://discussions.apple.com/thread/4282843

[Lanark]

Which app are you using?

Does this happen for all windows in all apps?