https://medium.com/@firstround/300-baud-modems-and-autonomous-vehicles-d15a983adb25 Chrome doesn't seem to APZ. Edge has a large amount of lag.

I don't understand how this page is doing that background image. There seems to be a div which has it as the background image, but that's display:none. And there's a canvas involved somehow. I think they found some new and "interesting" way to implement parallax scrolling.

Yes, they're moving the picture by drawImage'ing it to a position:fixed canvas. This is option 3 recommended by http://www.html5rocks.com/en/tutorials/speed/parallax/#toc-option3 . :(

So as far as I can tell there isn't even a visually observable parallax effect for the top image on this page. Scrolling up and down with APZ disabled everything seems to be moving at the same speed, so if they were trying to implement parallax it doesn't seem to have worked. Perhaps the code is just built into their publishing platform or something. Regardless if they want a parallax effect they can now use the CSS perspective property as described at http://keithclark.co.uk/articles/pure-css-parallax-websites/ to get compositor-driven parallax effects.

I don't get any lag when flinging this around on a retina MBP. Jeff, can you still reproduce (and maybe make a screencast if so)?

No issue for me too. :/ or maybe \o/

Name Firefox Version 47.0a1 Build ID 20160201030241 User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

I can still see this, although it's pretty hard to observe. The easiest way I think is to look at the gap between the top image and the start of the article text as you scroll around. The gap shrinks/widens a little bit. It's more observable on the URL https://medium.com/@samson_hu/building-analytics-at-500px-92e9a7005c83 (taken from the bug duped to this one) because on that page there's a caption just below the image, and so the gap changing size is more obvious.

Here's a screencast, look closely at the gap just below the image and above the "Photo credit" text.

Ah, now I see it. (And now I'm kinda dizzy...)

https://medium.com/message/the-tech-diversity-story-thats-not-being-told-9a36fb40530f#.mlu27rx9i is another very visible URL.

So Markus pointed out that newly published Medium posts don't seem to have a parallax effect any more. They seem to have realized that it doesn't work well and removed it. Older articles, like the ones linked in this bug, still have the (broken) parallax behaviour. Possibly they are using an older snapshot of their JS code while newly published articles use newer code. Given that, is there any point in reaching out to them? Presumably they have a reason for not updating their older articles to use their newer code.

I'm going to close this as WONTFIX as per comment 12. If someone feels strongly that we should reach out to Medium about their older posts, or take some other action, please feel free to reopen and make your case.