I want to achieve windowed functionality of Firefox's F11 fullscreen mode, where there's no window borders nor tab/url bar, which pops in on hover. Having every pixel actually be web space is just preferable to me. This used to be possible in old Firefox versions simply by resizing a fullscreened FF window using a resizer extension or window manager (such as seen here, with version 55.0.3: https://drive.google.com/file/d/1klHdUHiKtLVITmrQnul8O1zF32l-Uz6c/view). At some point, something must have changed in FF's fullscreen API because it no longer responds to any of this. I'm willing to pay anyone savvy enough to come up with a solution. Ideally by figuring out how to again be able to simply resize F11 windows. Note: "full-screen-api.ignore-widgets" isn't cutting it, there will still be a window border and the tab/url bar won't automatically pop up. Cheers.