Especially now that we have retargeting, stuff like propeller ads and other popunder traffic is a goldmine.. Propeller ads in 2018 shouldn't be used with the goal of getting conversions as that's wishful thinking. Firstly it's the most aggressive type of interruption marketing. It's akin to trying to seduce a woman that doesn't know you by jumping in front of her, screaming "SURPRISE", then continuously poking her hoping that she'll fall in love with you.. You come off as a creep, and extremely annoying. Not saying popunder traffic doesn't convert, as it does for some people. But this is only after they have tested a lot and identified sites that convert and is congruent with their offer.. An example of a site which has popunders that convert is flaticon.com. This site offers free graphic design icon assets. And each time an icon is about to be downloaded, a popunder leading to a highly contextual keyword triggered Shutterstock page opens. So if someone searched for football helmet icons, the free site has a limited amount of icons, but the popunder opens up shutterstock with a wider range and possibly more professional icons. Well they're doing affiliate to shutterstock which I don't think is the best offer to explain this, but at least it is congruent and well timed pop. Why does this work? Well this is a private popunder script so the site owner chooses which URL to pop, so it's not the same as running popunder campaigns on propeller ads where the publisher can't choose which url to pop as that's decided by the network's algorithm. The popunder only opens when someone downloads an icon. If someone downloads a free icon, they are likely to buy some graphic design assets as they're most likely needing a lot of assets. Also compared to popunder publisher sites which are mostly adult, hack or blackhat stuff, there aren't a million popunders popping at every click which is annoying and people are blind to. Like if you spend $300 which I guess shows your popunder to hundreds of thousands of people and you have 0 conversions, then something must be wrong with the whole system.. What should popunders be used for? Traffic to retarget. Extremely cheap AF traffic. I haven't used much platforms, but most of them offer a lot of targeting options. In terms of targeting options, I probably won't bother with topic or niche, but focus on device and location targeting buying traffic from porn sites. The reason for porn sites is most people don't use vpns or proxies for porn, compared to other sites you'd find on pop networks like streaming, movies etc and also most people use mobile devices, so the chance of getting bots or adblock is almost impossible I guess. Also everyone watches porn, so traffic is pretty much unlimited. Target by location to retarget with location specific offers and device for the same. Example scenario. I have an iphone related ecom site. I just simply go on plugrush or trafficjunky, target people using iPhone 5 on blah blah network in california and buy 100,000 visitors for £50 or something. Obviously the more variables, the less potential traffic. I don't send them to my store but just a random site with my retargeting pixel. Now run a retargeting ad with my offer + calling out the location and you have a formula for conversions. That's 100,000 potential customers acquired for extremely cheap.