Secret Chat is Telegram’s device-specific chat mode that uses end-to-end encryption. Unlike ordinary cloud chats, a Secret Chat is meant to be readable only on the two devices participating in that conversation. Telegram says it is not synced across all logged-in devices, which reduces exposure if one account session or server-side store is compromised.
For cyber security, this matters because the security model changes the threat surface. Secret Chats can help protect sensitive discussions from server compromise, bulk collection, and some forms of interception. But they do not stop endpoint compromise, account theft, screenshots, or abuse by the person on the other side. In real attacks and investigations, defenders often distinguish Secret Chats from public channels and cloud chats, since each mode leaves different evidence and creates different monitoring, moderation, and exfiltration risks.