Keyboard shortcuts usually helps us speedup our work, however some shortcuts are difficult to remember and use. In Firefox, there are several keyboard shortcuts and you can customize each onefor your own convenience. Here is a very simple add-on to close Firefox’s active tab by hitting ESC key.
Normally, you can close Firefox’s active tab by using Ctrl + W or Ctrl + F4 key combinations, but the EscCloseTab extension lets you simply close the active tab just with your ESC key.
If you have interested, you can install EscCloseTab from Mozilla add-on site.