Chromecast Audio Stream is described as 'Capture your system audio and stream everything directly to your Chromecast' and is an app in the Audio & Music category. There are seven alternatives to Chromecast Audio Stream for a variety of platforms, including Mac, Windows, Chromecast, Linux and Android. The best alternative is Airflow. It's not free, so if you're looking for a free alternative, you could try Airfoil or Videostream. Other great apps like Chromecast Audio Stream are Mkchromecast (Free, Open Source), AllCast (Free), chromecast.link (Free, Open Source) and go-chromecast (Free, Open Source).
Select any video from the Videostream extension for Google Chrome and, using the Chromecast extension, play it on your Chromecast. It's fast and simple to use. Videostream supports subtitles, MKV, AVI, MP4, playlists, and more.
This page makes use of the Chromecast sender API to control Chromecasts on your local network. It provides a web interface rather than requiring you to install a native app on your devices. Links you load are accessed directly by the Chromecast.