I think I should just remove the poster, it was initially replacing the GIF, which was megabytes in size. Given that the sizes of the WebP and WebM animations a

I think I should just remove the poster, it was initially replacing the GIF, which was megabytes in size. Given that the sizes of the WebP and WebM animations are pretty close I can live without it; all major browsers support both formats anyway. I cannot help with the caching fun here, quick tested in both Chrome and Firefox. There's probably something strange in the video tag, either by design or by implementation.