HTML Checking for Large Sites

Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.

Attribute “controlslist” not allowed on element “video” at this point.

controlslist
video
experimental

The controlslist attribute on the <video> element is experimental, and not yet valid in the current HTML5 standard, so you should use it with caution as it may not be supported by all browsers.

Learn more:

MDN: experimental controlslist
Can I Use controlslist?
HTML Living Standard: the video element