Two halves. The real bug: fullscreen kept an invisible titlebar band at the top, so the video never reached the screen edge - worst on vertical videos, which lost real height. Fullscreen is now truly edge to edge. For bars born of an aspect mismatch, Zoom to Fill (press z, or Playback menu) crops the video to cover the screen instead of letterboxing; it applies in the main window, mini, and fullscreen alike. The thin strip beside the camera housing is reserved by macOS itself. Requested by Nikolaï via email.