Firefox should be able to properly compute the height of the screen, so that's not good behavior. Sometimes inappropriate window and dialog dimensions can occur due to nonsensical values in a settings file. The file is hard to edit, so the general remedy is to remove it and let Firefox use default sizes. Here's how. Open your current Firefox settings (AKA Firefox profile) folder using either * "3-bar" menu button > "?" button > Troubleshooting Information * (menu bar) Help > Troubleshooting Information * type or paste about:support in the address bar and press Enter In the first table on the page, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows Explorer. Leaving that window open, switch back to Firefox and Exit, either: * "3-bar" menu button > "power" button * (menu bar) File > Exit Pause while Firefox finishes its cleanup, then rename '''xulstore.json''' to something like xulstore.old. If you see a file named localstore.rdf, rename that one to localstore.old. Start Firefox back up again. Do maximized windows display normally again? If you prefer the Menu Bar or Bookmarks Toolbar displayed, you'll have to turn them on again. You can use one of these methods to show the toolbar list and select the desired bars there: * right-click (on Mac Ctrl+click) a blank spot on the tab bar (or the "+" button) * (menu bar) View > Toolbars<br><em>On Windows, tap the Alt key to activate the menu bar temporarily.</em> * in Customize mode > Show/Hide Toolbars (see: [[Customize Firefox controls, buttons and toolbars]]) To turn on the Bookmarks Toolbar, Menu Bar, or other bars, click it on the list. This is also how you can turn off toolbars.