I hadn't noticed how static the Google Photos library was until Apple's iOS 13 announcement, when our favorite Android competitor showed off its improved Photos app with smarter navigation and live previews of videos, Live Photos, and more. After seeing that, each time I scrolled through Google Photos on my phone, I wished it could be as lively, and now it finally is... though there's room for improvement.
With version 4.20 of Google Photos, which started rolling out a few days ago, you'll see live previews of videos as you go through your library. The previews play automatically until the end and restart if the thumbnail is still visible. When the thumbnail starts going out of view, the video stops.
This only works for videos now. I'd like to see motion photos, specifically, supported, as I don't take a lot of videos but I do capture a lot of quirky little moments along with my regular still shots. I also hope it supports animations and burst photos in the future. Another caveat is that these previews autoplay in the main gallery view, but don't seem to in albums or search. And finally, this is only available on Android now. On the web, you have to hover over a video thumbnail to preview it.
If you'd like to give this a try, make sure you're on the latest Google Photos v4.20 and look for videos in your library.