Like your phone or tablet, your Chromecast stores personal information like your router name and password. Here’s how to reset it before you sell or give it away so that information doesn’t fall into the wrong hands.
Picture: ปรัชญา สิงห์โต/Flickr
Like any device, you should do a factory reset on your Chromecast before you sell it. The easiest way to reset your Chromecast to factory settings: plug it in and hold the only black button on the device down for 25 seconds. The Chromecast will start flashing when you can take it out. Plug it back in to double-check that your information has been erased.
Is it Safe to Sell a Google Chromecast Device? [How-To Geek]