What is it?
The free open source cross-platform wide-spectrum blocker / ad blocker browser extension UBlock Origin (uBlock Origin) by Raymond Hill (Gorhill).
Here is how Wikipedia describes this browser extension:
uBlock Origin (pronounced you-block /ˈjuːˌblɒk/) is a free and open source, cross-platform browser extension for content-filtering, including ad-blocking.
The extension is available for several browsers: Safari, Chrome, Chromium, Edge, Firefox, and Opera.[7]
uBlock Origin has received praise from technology websites, and is reported to be much less memory-intensive than other extensions[8][9] with similar functionality.[10][11]
uBlock Origin’s stated purpose is to give users the means to enforce their own (content-filtering) choices.[12][13]
As of 2017, uBlock Origin continues to be actively developed and maintained by founder and lead developer Raymond Hill.[14]
Here are the links where you can get uBlock Origin for several different web browsers:
uBlock Origin for Google Chrome & Brave Browser & Chromium
uBlock Origin for Mozilla Firefox
John Jr's Blog 