Instagram does not typically send text messages from a dedicated, consistent phone number. Notifications and security alerts are often dispatched using shortcodes or, more frequently, directly through the application itself. While some automated messages may originate from numeric codes, these are not designed for user replies or ongoing conversation.
The absence of a fixed number enhances security and reduces the risk of spoofing or phishing attempts. Relying on in-app notifications allows Instagram to implement robust security measures and ensure message authenticity. Historically, SMS was used more extensively, but the shift towards in-app communication provides a more controlled and secure environment.