Have latest version of Firefox...
Just installed Adblock Plus(12-31-17) ...
Tested it on Youtube--The main reason I got it
was to prevent preroll ads or any ads that interfere
with watching the chosen video...

It failed the test! I was so disappointed.

I immediately removed it.

Searched for alternative, found and installed AdBlocker Ultimate...

Tested it right away on Youtube...

Hooray! Worked like a charm!

Hope it will continue to do so, as I assume Adblock Plus worked well for some time.

very good!

很好，很强大

perfect!

Near the best. Some ads still live. Hope it's not an agreement with developer and advice companies!)

OK

Haben sich doch nun verkauft. Das Add-on ist nicht mehr zu gebrauchen. Es block so gut wie keine Werbung mehr.
Ich bin auf uBlock Origin umgestiegen.

This is a lousy adblocker which serves ads itself. Get this instead: https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

Using Firefox version 54 with Adblock version 3 or higher does not add menuitem to allow you to configure Adblock or turn it off on a per site basis. Version 2.9 still works ok

La gestione semplice dei filtri