Hmm, is Firefox using a significantly different resolution from other software on your system? That could be caused by "Compatibility" settings. To check for that, either: * Desktop shortcut: right-click the icon, choose Properties * Pinned taskbar icon: right-click the icon, right-click Mozilla Firefox, choose Properties Windows normally will select the Shortcut tab. Click the Compatibility tab. For best results, make sure no checkboxes are checked here. (Example screenshot attached.) ---- If the problem isn't throughout Firefox but a message from one or more websites, it could be an issue with a high zoom level. Firefox reports a lower resolution to sites when you are zoomed in more. To try zooming out, hold down the Ctrl key and tap the - key once or twice. (To enlarge again, hold down Ctrl and tap the + key.) Does that make any difference? You might need to reload the page (Ctrl+r) to trigger their recognition of the change.