If you take a look at the source[0], you'll notice they roll their own viewport renderer, presumably as a way for them to do their "tracking pixels". I imagine

If you take a look at the source[0], you'll notice they roll their own viewport renderer, presumably as a way for them to do their "tracking pixels". I imagine this might be what causes the difference in behavior? If anyone more knowledgeable could jump in, that would be cool. [0] https://github.com/ampproject/amphtml/blob/master/src/viewport.js https://github.com/ampproject/amphtml/blob/master/src/viewpo...