I want to add a pop under ad on my Adsense site

Same here. But I think the word is just cautionary.

Too many people come here and start a thread about losing adsense.
In fact, I'd say the people that start threads about "what ifs..." are
usually looking to tweak the rules. Otherwise, why ask?

Google does make it clear to not try and tweak them. Even if they
do not spell out everything, which they can't, don't take it to mean
that it's okay.

On the surface, a pop under that does not interfere with the site
navigation, which includes surfing out, and does not block the ads
may be okay. But it's got to be borderline. I would not chance it.

Any pop-up, pop-under, whatever you have it, probably takes a new
click to surf away, or at least takes an extra second or two to get
away. If the pop under covered any part of the site, that to me would
be a violation. If the pop under shrunk the site, that too would interfere
with the navigation.

But again, point taken on the "if" part. I just can't come up with a scenario
where a pop under would not interfere at least slightly with surfing in and
out of the site. Not everybody has the same resolution. What may not be
covered on your screen may be covered on mine.

I mean, are you wanting people to click adsense or a pop under ad?
Or even read a pop under?

I'd err on the side of adsense.

I can't come up with a scenario where I would even want a pop under
on an adsense site.

Paul