When you spend a lot of time in front of your computer, many small actions performed repeatedly can add up to a lot of wasted time. The worst of these small offenders is the copy and paste… so how can we simplify this in Firefox?
The AutoCopy extension will automatically copy to the clipboard any text you select, and allow you to paste it with a middle click anywhere in Firefox.
All you have to do is select the text you want to copy, and it will be copied to the clipboard right away.
You'll notice the new icon in the status bar, which will let you change a few options or open up the full options panel.
There's lots more options in the options panel… you'll notice the keyboard shortcut options as well.
Once you get used to this extension, you'll wonder how you lived without it
Source-howtogeek