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This document is a WORK IN PROGRESS.
This is just a quick personal cheat sheet: treat its contents with caution!


xmodmap is a program used to edit and display the keyboard modifier map and key map/table that are used by client applications to convert event keycodes into keysyms.



A modifier key is a special key (or combination) on a computer keyboard that temporarily modifies the normal action of another key when pressed together. By themselves, modifier keys usually do nothing; that is, pressing any of the Shift, Alt, or Ctrl keys alone does not (generally) trigger any action from the computer.


There are two types of keyboard values in Xorg: keycodes and keysyms.

keycode: The keycode is the numeric representation received by the kernel when a key or a mouse button is pressed.

keysym: The keysym is the value assigned to the keycode. For example, pressing A generates the keycode 38, which is mapped to the keysym 0×61, which matches a in the ASCII table. The keysyms are managed by Xorg in a table of keycodes defining the keycode to keysym relations, which is called the key map table. This can be shown by running xmodmap.

Table of contents


# emerge -a xmodmap
# pacman -S xmodmap
# apt install xmodmap
# yum install xmodmap
# yum install xmodmap


Create a xmodmap config file, a custom key map/table, and load it when starting your X session:

$ vi ~/.config/Xmodmap
    > ! this is a comment
    > ...

$ vi ~/.xinitrc
    > ...
    > [[ -f ~/.config/Xmodmap ]] && xmodmap ~/.config/Xmodmap &
    > ...


Print the current modifiers:

$ xmodmap -pm

List keycodes and associated symbols (key map table formatted into expressions):

$ xmodmap -pke


Each keycode is followed by the keysym it is mapped to. For example keycode 57 = n N indicates that the keycode 57 is mapped to the lowercase n, while the uppercase N is mapped to keycode 57 + Shift.

Each keysym column in the table corresponds to a particular combination of modifier keys:

  • Key
  • Shift+Key
  • Mode_switch+Key
  • Mode_switch+Shift+Key
  • ISO_Level3_Shift+Key
  • ISO_Level3_Shift+Shift+Key

Not all keysyms have to be set, but to assign only a latter keysym, use the NoSymbol value.


To identify X11 input keycodes, the xev utility can be used. Just run $ xev in your terminal and enter the key in order to get its details. A lot of information will be output, with the following command you can start xev and show only the relevant parts:

$ xev | awk -F'[ )]+' '/^KeyPress/ { a[NR+2] } NR in a { printf "%-3s %s\n", $5, $8 }'


There are predefined descriptive keysyms for multimedia keys, e.g. XF86AudioMute or XF86Mail. These keysyms can be found in /usr/include/X11/XF86keysym.h. Many multimedia programs are designed to work with these keysyms out of the box, without the need to configure any third party application. Also, note that available keysyms depend on the xkeyboard settings (see $ man xkeyboard-config for more details).

Test temporary changes, e.g. replace a by e (a keysym will be translated to e keysym):

$ xmodmap -e "keysym a = e"

Test temporary changes, e.g. assign different keysyms to keycode 24:

$ xmodmap -e "keycode 24 = e E e E"

Test remanent changes, i.e. changes made in the xmodmap config file:

$ vi ~/.config/Xmodmap
    > ...
    > keysym a = e
    > keycode 24 = e E e E
    > ...
$ xmodmap ~/.config/Xmodmap


  • Reverse pointer buttons:

    $ xmodmap -e "pointer = 3 2 1"

  • Reverse scrolling:

    $ xmodmap -e "pointer = 1 2 3 5 4 7 6 8 9 10 11 12"

  • Turn caps lock into control:

    $ vi ~/.config/Xmodmap
      > ...
      > clear lock
      > clear control
      > keycode 66 = Control_L
      > add control = Control_L Control_R
      > ...

  • See xmodmap man page's example section for more examples.

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