Walking down Abbot Kinney Boulevard, the retail strip in Venice, California, can feel like scrolling through Instagram.
Why did I see that my contact joined Signal? They just see a number they know is registered. If someone knows how to send you an insecure SMS, we want them to see that they can send you a Signal message instead.
Nothing is sent to them by your Signal app or the Signal service.
People who already know your number and already have you in their contacts see that they can contact you on Signal. Why did someone see that I joined Signal? Once your phone knows which of your contacts is a Signal user, it can optionally notify you when a new contact has started using Signal.
Signal developed a private contact discovery process that enables Signal clients to efficiently and scalably determine whether the contacts in their address book are Signal users without revealing the contacts in their address book to the Signal service. How does Signal know my contact is using Signal? Registration notifications are never transmitted by anyone in any direction at all these notifications are created by your phone. The Signal service does not have any knowledge of your contacts. Signal does not send your phone number to anyone unless you send them a message or make a call to them. Does Signal send my number to my contacts?