Frequently Asked Questions
macOS includes a feature called secure text input which prevents other apps from capturing keystrokes (while you're in a password input field in Safari, for instance). If you're using Command-Tab to activate Witch, you'll find it doesn't work when secure text input is active -- that's because we can't trap the Command-Tab keystrokes while secure text input is active.
As soon as you click out of the password box in Safari, Command-Tab will again work to activate Witch. Note that other apps may use secure text input in a more aggressive manner, and Command-Tab may not work at all when in such apps (I don't know of any such apps at this point, though).
Another common cause of this issue is Terminal: if you have Terminal > Secure Keyboard Entry enabled, then Witch will fail to activate with Command-Tab. That's because OS X prevents us from grabbing the keystrokes as they're typed.
Another possible source is 1Password: Command-Tab for Witch will work fine if it's visible, but if you hide 1Password, it then activates Secure Text Input, and Command-Tab will stop working.
The only permanent solution to this problem is to use different activation keys for Witch -- the method we use to trap everything but Command-Tab works when secure text input is active. (The reason we need two methods is that Command-Tab is used by the OS, so we have to capture it differently than we do the other activation keys.)
If you're trying to assign Command-Tab and cannot do so, you're also being blocked by Secure Text Input. You can try quitting all apps, which will then let you assign Command-Tab ... but if/when Secure Text Input mode is activated in the future, Command-Tab will bring up the normal Mac app switcher instead of Witch.