Short answer? It’s shift+f to toggle through the three different modes.
If you’re here, it’s because you simply want to know how to use Lightroom in full-screen mode. Inexplicably, virtually every answer on the web shows you only how to full screen a single photo. Which is not hard to do (just press ‘f’).
But using full-screen for the application works wonderfully, and is my preferred way to use the application. It’s a little awkward to figure out how to use it, though.
I believe this works on both Lightroom Classic and Lightroom CC, but if you find that’s not the case, let me know in the comments and I’ll update it.
So how do I full-screen Lightroom?
You just press shift+f to toggle through the three different screen modes.
The mode you start on is generally just like any application and how it normally is.
The second mode, frankly, doesn’t do much other than reduce the size of the header in Lightroom, giving you a little more space to work with.
The third and final mode is the only truly “full-screen” mode that allows you to continue editing your photos. The full editing interface is still available, but almost everything above and below your image, including everything from Windows, is hidden.
And that’s really all there is to it! To return to the default, just keep toggling through the modes using shift+f until you reach it.