FWIW, we can't force the controls attribute as it may as the video may already have controls even if it has the autoplay attribute. We are looking into dropping the autoplay restriction when Data Saver is enabled and this should make things a bit better as <video autoplay muted> would work and this issue is particularly problematic on these videos.

As mlamouri said, most sites disable controls in order to add their own. It is up to the site to ensure that users have some way of starting the video if they choose to disable Chrome's logic. This is working as intended.

I understand your point. However if there is no way to detect in JS that Data Saver mode is on, it's impossible for the developer to conditionally display the controls, is it? There are many situations where you want do display a muted video without controls.

FYI, I initially posted a comment on GitHub here: https://github.com/w3c/battery/issues/9#issuecomment-358309992 but it seems impossible to detect power saving mode. 

You can check whether the play promise gets rejected. If so, you will know that autoplay is blocked and you need to add controls. Here is a bit of pseudo code to get you started:

var promise = document.querySelector('video').play();

if (promise !== undefined) {

  promise.then(_ => {

    // Autoplay started!

  }).catch(error => {

    // Autoplay was prevented.

    // Show a "Play" button so that user can start playback.

  });

}

Thank you for the snippet. I had not thought of this approach.