When Apple launches its next version of the Mac operating system, OS X El Capitan, the company will integrate true Airplay on a system level. This will allow you to push YouTube, Vimeo and other services wirelessly to the TV via Apple TV.
True Airplay in OS X El Capitan
As you probably know, Apple’s Airplay consists of two components when talking about video. “Airplay Mirroring” can mirror the whole desktop and “Airplay” lets the Apple TV box take over the stream, for example to YouTube’s servers. In 2012, Apple added Airplay Mirroring to the Mac with the release of OS X Mountain Lion.

With the next version of OS X, Apple will add true Airplay that ensures best possible quality from the streaming service. It lets you push for example YouTube from your Mac wirelessly onto the TV screen via Apple TV and continue to use the Mac for other tasks without interrupting video playback.
It is even possible to push streaming video to the TV screen from the Mac via Airplay while playing another video on the Mac screen. Once video starts playing on Apple TV you can rewind or pause with the Apple TV remote. Airplay on Mac works only in Safari.
Works with YouTube & Vimeo
FlatpanelsHD has taken a closer look with the public beta of OS X El Capitan. It is clear that Airplay is integrated deep into the operating system. It already works with video services such as YouTube and Vimeo. Below you can see how it works with YouTube. Notice the small Airplay icon in the lower right corner.

It does not seem to work with subscription streaming services yet, possibly because the video streams are encrypted. We experience problems with Netflix on OS X El Capitan so we cannot check for this particular service. It is possible that premium services need to add support during development.
With the release of OS X El Capitan, Mac users will get one of the popular features from iPhone/iPad but it is also a sign that Apple continues to focus on Apple TV. OS X El Capitan is expected to be released this fall. If you are eager to try it today you can join Apple's "public beta" here.