The best AdBlocker on the market, hands down.

The best adblocker for Firefox and there is very little reason to use anything else. It is open source, has blocklist customization, supports blocking annoyances and trackers as well as ads and it will never ask for or require micro-transactions.

best blocker ever!

Ublock is amazing. I haven't seen an ad in so long! It makes my whole experience safer. It's quite simple to customise (I've never used the advanced settings though as I am definitely not an advanced user). I appreciate this extension and the people who make the filter lists so much.

Haven't seen an ad, or a website detecting I have an adblocker. The only thing I've seen is a website saying "an ad used to be here", but those might've just been placed behind the ad and not a sign of the adblocker being detected.
Youtube does sometimes detect you have an adblocker, but it's always fixed within a week. Even then, them purposely making your video load 5 seconds slower is less annoying than a 30 second ad.