Log in to see the same chats on every device. This is optional.
Without an account your chats are saved only on this device. Log in on any device to see the same history there.
Accounts and synced chats are stored in your own free Firebase project (about 3 minutes):
rules_version = '2';
service cloud.firestore {
match /databases/{database}/documents {
match /users/{uid}/chats/{chat} {
allow read, write: if request.auth != null
&& request.auth.uid == uid;
}
}
}