Users will get better contrast, improved brightness levels, and images sharper than HD once that happens. If you're less concerned about the content being good, as well as looking pretty, you can also buy Suicide Squad in 4K HDR. However, unlike Chromecast Ultra, Google has not made it clear whether Play Movies & TV service would support both the HDR formats. As long as your internet is strong enough (Googs recommends a consistent download speed of at least 15 Mbps) and a compatible TV, your device will be able to stream 4K UHD titles.
The HDR rollout is being enabled via support from two major studio partners, Sony and Warner Bros., the company says. Google isn't releasing a comprehensive list of what's available; it's up to you to look. Current choices include Kong: Skull Island, The Lego Movie (and The Lego Batman Movie), Mad Max: Fury Road, Suicide Squad, Fantastic Beasts and Where to Find Them, and a mix of older stuff. It's available to start in the United States and Canada, and Google says it's available via the Chromecast Ultra as well.
Google follows its competitors like Amazon and Netflix, which have also slowly adopted the format and offered content over the past couple of years. As you might know, HDR makes the picture more authentic and vivid with more colorful representation. They will need to have a TV that has HDR support or a smartphone.