Your friends can now easily cast videos to your Chromecast thanks to a new feature called guest mode. The new mode allows anyone in the room with an Android device to jump on your Chromecast — even if they're not connected to your Wi-Fi network. Enabling guest mode on your Chromecast is just a few taps away.

How to enable guest mode in the Chromecast app:

  1. Tap Devices, select your Chromecast.
  2. Tap Guest mode.
  3. Slide guest mode to On.

That's all there is to it! Guest mode is available to anyone running Android 4.3 or higher (no support for iOS).

Source: Google Chrome Blog