Guests need your Wi-Fi. Google has dropped Chromecast's guest mode, so guests now join your Wi-Fi to cast. A guest with an Android phone can also use The Remote, which needs no account. They join your Wi-Fi and enter the code your TV shows. The Remote also has its own Guest mode, which limits the remote to navigation, play/pause and volume.
Chromecast guest mode is no longer supported
Google's help page says it plainly: "Guest mode is no longer supported. Guests can cast content from their Android or iOS devices by connecting to the host's Wi-Fi network." Google: guest mode That old feature let people cast to older Chromecasts without joining your Wi-Fi. It ended in 2023, and it was never part of Chromecast with Google TV. 9to5Google
Guests can cast once they're on your Wi-Fi
To cast from YouTube or another Cast-enabled app, a guest's phone has to be on the same Wi-Fi as the TV. That's Google's own advice above.
A guest can use The Remote with no account
The Remote doesn't ask anyone to sign up or sign in. A guest with an Android phone (Android 8.0 or later) joins your home Wi-Fi, installs The Remote from our site, picks the TV and enters the code it shows.
The Remote's Guest mode limits the remote to the basics
The Remote has a Guest mode. When it's on, the remote is limited to navigation, play/pause and volume, and the screen says "Guest mode is on". To exit, hold the TV name at the top for 1 second.
Where The Remote fits
The Remote is a free phone remote for Android TV and Google TV devices with Android TV Remote Service v2. That includes Google TV devices that support the Android TV Remote Service, such as Chromecast with Google TV and Google TV Streamer. No ads, no account. There's no iPhone version.