I found that this add-on interfered with several websites that I used regularly. One was the Washington Post site. Also NYTimes and IMDB. When I turned off PopUpOFF, things on these sites went back to normal.

I can't say that this app is the only contributor to my problems, as I have other add-on blockers installed as well. Also the problems I had with websites evolved over time, so there may have been contributing causes from website changes. But when I stopped this add-on, problems disappeared.

The developer responded that there was "confusion" about how the addon works. When I go to the Washington Post website with PopUpOff installed, the entire page fails to show up. Then I halt the addon, and the Post page goes back to normal. That not confusion about how the addon works.

I appreciate those who develop addons. I use a bunch of them. Some just don't work, at least not on my browser. My review noted the possibility of other causes of interference. I gave a balanced review of my experience. It's not confusion.