If I press the keyboard shorcut Cmd-Opt-Shft-Ctrl-W from any app it seems to flash my entire display. I believe this started with Catalaina but I could be wrong.

I thought at first it was Keyboard Maestro doing it but the shortcut flashes my display even when Keyboard Maestro is not loaded.

Any ideas what Cmd-Opt-Shft-Ctrl-W does and why it flashes the screen?

  • The same thing happens to me. It looks pretty similar to the screen flash you get in System Preferences -> Accessibility -> Audio -> Test Screen Flash. – beninato Dec 10 '19 at 19:20

Quoting from this question:

WifiDiagnostics files filling up drive even with logging disabled

... that particular keyboard shortcut, command+option+control+shift+w, triggers something in OS X (possibly Catalina only; I don't have an older OS to test against) that starts the wifi logging.

So please check your /private/var/tmp.

  • 2
    My /private/var/tmp was filled tihe WiFiDiagnostic files. I have muscle memory for ctrl-cmd-opt-shift-W. – Scott Walter Dec 12 '19 at 15:51

The combination Cmd-Opt-Shft-Ctrl-W is some kind of system reserved combination, e.g. during updates/installs of the OS Cmd-Opt-Shft-Ctrl-W opens up a GUI for the update process, including access to the update log. So it may act as a "breaker" for the system itself. As @ankii suggests, it triggers network diagnostics when booted, so the screen flash is there as to notify that the indeed diagnostics were triggered.

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