Whenever I resize a Safari window to the size and position I want, it eventually expands back to fill the entire screen from edge to edge. It is not macOS full-screen mode, but the window becomes much larger than intended. This happens whenever I open a new Safari window and sometimes when I switch back to a window that is already open. The behavior only started recently, and restarting the Mac did not fix it. I often keep phone mirroring and Safari open side by side, so constantly resizing Safari is becoming frustrating. What could be causing this, and how can I troubleshoot or stop it?
2 Answers
A restart is worth trying for odd window-management glitches, but since that did not help, I would watch for accidental double-clicks on the title bar or a window-management utility that may be resizing Safari. Temporarily quitting those utilities and testing Safari by itself could help narrow down whether the behavior comes from macOS or another app.
macOS generally remembers the size and position of an app's most recently closed window. If the last Safari window was expanded, new windows may reopen that way. Also check whether the title bar is being double-clicked accidentally, since that toggles the window between its current size and a larger size. One workaround is to create standalone Safari web apps for frequently used sites through Safari's File menu. Each web app keeps its own window size and position, separate from the main Safari windows.
I understand how macOS is supposed to remember window sizes, but that does not seem to explain this behavior. Safari keeps expanding even after I resize it, so I have to correct the window manually over and over.