How can I stop the left alt key opening the application menu on Ubuntu 18.04?

Question

I have Ubuntu 18.04 installed with GNOME.

My left alt key opens application menu while right alt works as expected (left alt + F4 doesn't work for example, right alt + F4 works perfectly).

How can I fix the left alt behavior so that it works like right alt?

Solution

The terms we are discussing here are "keyboard shortcuts" and "keybindings". They are useful when searching for help.

First, run xev in a terminal to see if the key works.
If it works, open Settings > Devices > Keyboard for a list of shortcuts. If it says Alt without specifying right or left they should both work. Replace any that specify a side and make sure it only says Alt.

If you have trouble making the settings do that, install dconf-editor

sudo apt install dconf-editor

and launch it from the terminal

dconf-editor 

Locate the search icon and type keybinding and look through the paths for what you need. In your example navigate to

org/gnome/desktop/vm/keybindings/close 

If the default value is on it should be set to

['<Alt>F4']  

If it's not, switch default to off and enter exactly the above as a custom entry.

My Alt shortcuts seem to be the same for each side, so maybe yours got reconfigured somehow.

Comments

[damadam]

i'm not sure you really want the same behavior between left and right Alt; the right isn't called Alt Gr for nothing, it's because he has a behavior that the basic Alt hasn't; for example, if Alt Gr would have the same behavior as Alt, on an azerty keyboard, we couldn't type characters like '@', '{' or '#' (and i'm pretty sure it can't be possible to type some character too on a qwerty keyboard) and think about the character which can be displayed by typing the ASCII code

[Dave Jarvis]

See also: bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1508146 for a bug regarding Alt+Left and Alt+Right. The fix is: sudo kbd_mode -s

[ingvar]

Close combination is set to['<Alt>F4'], but on alt press window losts focus. If restore focus (click in window) F4 works and closes window.

[jordy]

What happens when you quickly tap left Alt and nothing else? What happens when you hold it down for a couple seconds? (Make sure some windows are open)

[jordy]

Also, install Gnome Tweak tool. Under Keyboard & Mouse -> Overview Shortcut -> Additional Layout Options. Explore that and see if left Alt is set to anything. It's possible that a "hide window on focus loss" setting is enabled, possibly because the Alt_L is activating the top bar.

[ingvar]

Quick tap on left alt opens application menu. On holding alt active window losts focus. And I don't have any combinations with Alt