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Regular app called weblock works great

I wouldn't trust weblock. Some bad reviews there.

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Adblockernetworks seems to be working for me. I don't recall ever seeing ads in the 6 months I've been using it with YouTube.

repo.yllier.net and it's free.
 
I just use adblock but have an older version of the YT app installed - you can roll back by using something like AppAddict.

It works for me, I don't like the new update anyway because it dims the whole screen for a few seconds at the beginning of a vid and also the play/pause button is center screen and not lower corner which is a pain on an iPad.
 
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