if someone find my telegram chat ID (instead of my phone number or username), what can do with that?
is it dangerous?!
is it a big deal that someone can find my ID? should I worry about it?
If someone with a (user)bot wants to send you a message, they can do that via the userID only. But only if they have "seen" you. Seeing you is considering their client to receive a message from you, be it in a private message or group.
Bots can only send you a message if you have started it in a private chat, otherwise they can only send you a message in a group they share with you.
So there is no real risk of people knowing your ID.
what can be done by a telegram chat ID?