Cloud Storage and Deletion: Your synced contacts are stored in the Telegram cloud (encrypted) and can be deleted from Telegram's servers at any time via your privacy settings (Settings > Privacy and Security > Data Settings > Delete Synced Contacts).
4. Emphasis on "Cloud Chats" and Secret Chats:
Cloud Chats (Default): Most Telegram chats are "cloud telegram number database chats," meaning they are encrypted in transit (using MTProto) and encrypted at rest on Telegram's distributed servers. The encryption keys are also split and stored in different data centers in different jurisdictions. While Telegram could theoretically access these (as they hold the keys), their design minimizes the ability for any single engineer or authority to access all data. This cloud storage enables seamless multi-device sync.
Secret Chats (End-to-End Encrypted): For the highest level of privacy, Telegram offers "Secret Chats." These are end-to-end encrypted (E2EE), meaning only the sender and recipient have the keys to decrypt the messages. Telegram's servers cannot access the content of secret chats. These chats are device-specific and do not reside in the cloud. This highlights a deliberate choice to offer E2EE for sensitive conversations, even if not the default for all.
Business Model: Telegram's stated business model is not based on selling user data for advertising. This commitment is a core aspect of its privacy-by-design philosophy, distinguishing it from many other "free" messaging apps.
Minimal Data Storage: Telegram claims to only store the data absolutely necessary for its service to function. This includes phone numbers, user IDs, usernames, and profile information, as well as cloud chat data (encrypted). IP addresses and device information are also collected, but Telegram states it does not log timestamps/IP addresses related to individual messages.