It works great for me, although with the current Firefox there is a slight glitch. After installing the extension I clicked on the icon and got a blank white php page. I closed the tab and then clicked on the icon again and now the extension seems to work as expected.

It does what I need, and it works fine!

Nimbus Screen Capture, is just what I need to simply take necessary screenshots of websites.
And for those who have reviewed before me a grumbled about the loss of the copy function - read this:
"Current versions of Google Chrome and Mozilla Firefox prevent apps from copying pictures to clipboard."
A simple workaround is that you can simply right-click on the picture you see on the screen and select "Copy image".

Goes great with Nimbus note ( their free note taking cross-device app )

es la mejor de su tipo, muy fácil de usar y una ves que lo empieces a hacer te será indispensable.

La uso día a día y realmente es muy útil. Espere ansioso la nueva versión compatible con Firefox 57 con soporte para multiproceso.