Lost Access: If you lose access to your Telegram account (e.g., you get a new phone and can't log in), your registered phone number is a crucial component for account recovery.
Two-Step Verification (2FA): Your phone number is tied to Telegram's 2FA system. Even if someone obtains your SMS login code, they cannot access your account without your 2FA password, which provides a robust layer of security.
Contact Discovery and Connection:
"Find Your Friends" Feature: If you choose to enable telegram number database the "Sync Contacts" feature, Telegram securely uploads the phone numbers from your device's address book to its servers. It then compares these numbers against its database of registered users to identify which of your contacts are already on Telegram. This allows your in-app contact list to be automatically populated, making it easy to connect with people you already know.
"Contact Joined Telegram" Notifications: This feature, reliant on synced contacts, allows Telegram to notify you when someone from your phone's address book (who wasn't previously on Telegram) creates an account.
Spam and Abuse Prevention:
Deterrent: Requiring a unique, verifiable phone number for registration acts as a significant deterrent for mass spammers, bots, and malicious actors. Acquiring and maintaining a large number of unique phone numbers for spamming is far more costly and difficult than creating countless email addresses.
Accountability: While Telegram emphasizes privacy, the link to a phone number provides a fundamental layer of accountability, which can be essential for identifying and taking action against users who consistently violate Telegram's Terms of Service (e.g., engaging in illegal activities, harassment, or severe spamming).