The clipboard doesn't store anything to the hard drive, there is no clipboard location, and it's not saved anywhere.   If you turn off your computer, copy something else, the memory is replaced with the new memory. When you've taken a screenshot and clicked 'Save', you'll find it in your designated folder (like e.g. 'Downloads')

You can paste the image to to image editor. If you want to save the screenshot image then click the Download button and the image wil be saved to the default download folder.

See also:

• https://support.mozilla.org/en-US/kb/firefox-screenshots

Where I said in my post  :

When you've taken a screenshot and clicked 'Save', you'll find it in your designated folder (like e.g. 'Downloads')

You will see explained in this article :

https://screenshots.firefox.com/

^That is not correct.

If you click Save then the image is saved to a specific page in internet under a special GUID folder as set in about:config. If you would reset Firefox or reset your preferences then you will probably lose these saved images.

If you click Download then the image is saved on your computer and you see the Download button getting animated and highlighted.

Yeah, I know that this can be confusing: download something that isn't coming from internet and saving is saving to internet. The Firefox developers sometimes are hard to follow.

@ cor-el :

You're right : just now I wanted to prove you wrong, but indeed I had to click on 'Download' in order to find it in my Downloads folder.

(Took a screenshot earlier without clicking 'Downloads' and found it in my designated folder - guess that was just a 'lucky shot')