Video blocking test suite

As of 2018, modern web browsers block autoplaying video with audio to save battery power and ISP data charges.[1] However, they allow muted video to play automatically for pragmatic reasons. If browsers blocked muted video from playing automatically, websites would fall back to still image codecs that have even worse compression when used for animation. These codecs include GIF, JPEG, and PNG, and some playback techniques don't even use JavaScript.[2] So if you want to develop a browser extension that blocks all autoplaying animation, you'll need to ensure all these methods are blocked:

New 2018-07-25:

[1] "Hate noisy autoplaying videos? Google Chrome will finally block them by default" by Liam Tung states: "Google's policy allows autoplay if the video is muted or doesn't have audio", citing Chrome and Chromium blogs (source 1, source 2, source 3, source 4, and source 5).

[2] "CSS Sprite Sheet Animations with steps()" by Guil Hernandez