Using the Google Home App
1. Open the Google Home app.
2. Tap the Chromecast device.
3. Tap the gear wheel in the top-right corner of your device's screen to open the Device settings dialog.
4. Scroll to the bottom of the menu and tap Remove device > Factory reset > Your Chromecast and tap Factory Reset.
Using the Chromecast Device
1. With the Chromecast device plugged in, locate the button located on the side of the dongle.
2. Press and hold the button and wait for the device's LED light to begin blinking orange.
3. Continue holding the button down until the LED light turns white. Release the button and the Chromecast will begin the process of reverting to its factory settings.