I am aware of the built-in firefox screenshots, but they require the use of the mouse and at least 3 clicks.
This is one of several reasons why I never bothered to use Firefox Screenshots.
If you are looking for a single keyboard shortcut that triggers a file to be saved with your image, your best option is using operating system keyboard shortcuts. These vary between operating systems but are still fairly easy to remember.
Windows 10:
Take screenshot of the entire screen and save it to %userprofile%\Pictures\Screenshots
.
Windows+Print Screen
macOS:
Take screenshot of the entire screen and save it to the desktop.
⌘+Shift+3
Which OS are you using? – Mr Ethernet – 2019-11-26T16:22:36.097
windows and linux. on linux, i can get a window only screenshot, that is good enough – josinalvo – 2019-11-26T16:25:41.037
ideally I would prefer a solution that works on Firefox on any operating system – josinalvo – 2019-11-26T16:26:10.857
1You don't need the mouse (from an accessibility point of view that's important). Ctrl-Shift-S and tab gets your there. Just setting the record straight, I know it doesn't answer your question ;). – Eduardo Trápani – 2019-11-26T20:24:11.843