With using native controls we will get UX consistency, built-in accessibility,Volume, Chromecast, AirPlay, Closed Caption, etc..

There are issues with using native controls in IMA, that need addressing however:

1- Initially native controls need to be hidden and a custom "play" icon for click to play need to be present to capcture user-intent and initialize IMA.
2- During Ad play, controls need to be hidden since there is no way to disable "seek" otherwise.
3- Native controls Fullscreen is a big issue, outside of iOS, IMA needs to have a different Ad container rather than the <video> itself to go to fullscreen so various Ad formats can be served. There are two approaches for this:

• In Chrome, we can hide the native fullscreen with video::-webkit-media-controls-fullscreen-button { display: none } and provide our own button.
• In FF/IE, since we are in an iframe, we can toggle iframe's allowfullscreen attribute which automatically removes the native fullscreen control from all <video>s inside the iframe.