It kind of defeats the object if you get a deny/allow window come up in place of a popup.

Disappointing as it will not remember to deny sites you already denied.. so I have to deny 2-3 times for a single site. Not well written it needs to remember sites for denying.

It does'n work against "exit intent popup", so it's almost unuseful.

Stop to work... after last firefox update i have popups all time.

Pales beside Pop-up Controller.
Pop-up Controller was a click-on-click-off (toggle) Extension that just worked and worked just that simply--click on, click off. No opening a menu every time one wishes to block or unblock a pop-up. On some sites, pop-ups have to be allowed in order to download applications, updates, firmware, etc. Popup Blocker (strict) is just too much of a hassle compared to Pop-up Controller. Unfortunately, Pop-up Controller won't work with the newer versions of Firefox; so, in moving forward, we are forced to take a step backward.

Modify Popup Blocker (strict) to it as simple to use as Pop-up Controller, with the toggle on/off option, and maybe I'll use Popup Blocker (strict).

Too strict most of the time. Blacklist mode sometimes doesn't work.

Better to add a shortcut to add a domain to blacklist. Or at least add a link to open the options. Otherwise it's really wearisome to add blacklist item.

Disabled the add on most of the time. What a shame.

with latest 55.0.x I have only white pages in more sites... pity

For example, this vid streaming site keeps creating popup windows which can't be blocked by this add-on: https://fmovies.is/

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I think you need to review your add-on, your ideas are great, but it's not user friendly as enough (my opinion).