WARNIING ....
becarefull DO NOT INSTALL it scam that play videos in background for profit it fake add on
you dont beleve there are prof a research by Bryan Campbell is full detailed how this works
here is link:
https://malwaretips.com/threads/fake-minerblock-extension-repeatedly-playing-videos-in-the-background.78859/

RICK IS OUT.

makes Firefox slower. features are slow, difficult to use; parts of sites do not load or appear wrong. REPORTED.

do not block pirate bay

About two days after I installed this add-on, today suddenly my computer started freezing time and again, freezing so much I had to shut him down by unplugging the power cable!
I started to examine everything, hardware, software and it showed that Firefox was the culprit!
As nothing else was different or new or updated than the days before, I concluded, minerBlock must have done that freezing.
I deleted it and - oh wonder - Firefox works fine again.