I'm using iterm2 together with tmux and I need the function keys. Ever since I got the TouchBar Macbook Pro and upgraded to HighSierra, the F4 key became disfunctional in iTerm2 and emacs.

  • The F4 key is used to cycle through the open tabs in tmux forwards
  • The F3 key (cycle backwards) and in fact all other F keys work as expected
  • The F4 key worked before the HighSierra / Touchbar upgrade. I used Time Machine to migrate, so no configuration changed.
  • The F4 also does not work with on an external Magic Keyboard, indicating a software / mapping issue.

I suspect that some change in High Sierra makes macOS not pass the F4 key on to applications, but I'm not sure. I have checked that no system wide keyboard shortcut is assigned to F4. What else could I check?

Update: The issue can be confirmed with the keyboard viewer, a program that allows to display all keys pressed. It clearly confirms that all keys except F4 are registered by the system while F4 is not.


I have seen elsewhere that some key combos stop working until you reinstall iTerm2. If you have homebrew and cask installed, you can use brew cask reinstall iterm2.

(I'm so unsure about the efficacy of this that I would have posted it as a comment, but I can't comment yet)

  • turns out it does not depend on iterm2. It also happens in emacs. – Thomas Dec 4 '17 at 9:05
  • How about in native Terminal.app? (Hey, I can comment on my own answer!) – Jan Gronemann Dec 5 '17 at 9:26
  • It was system wide. The F4 key did not register anywhere. I confirmed it using "keyboard viewer" as described in the question and solved it as in my answer. – Thomas Dec 5 '17 at 9:55

I found a (weird) solution here. This could be some arcane migration bug that is present in MacOS for very long time. The linked thread is from 2011. Here is what worked for me.

  1. Backup your keyboard shortcut preferences (i.e. write them down)
  2. Delete the file ~/Library/Preferences/com.apple.symbolichotkeys.plist
  3. reboot
  4. Set up keyboard shortcuts in preferences as desired
  • Not work for me... at least, with this reset I got all new shortcut from sierra... work with <fn> + <cmd> + <f4> – heralight Mar 4 '18 at 6:04

Apparently it's related to safari and / or chrome, and / or gmail / inbox https://discussions.apple.com/thread/7813416

a quick fix: +Q on safari and chrome, wait 30-40s, test it...

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