Session continuity is the mechanism that keeps a user logged in as they move between devices, browsers, or apps. Instead of forcing a new sign-in every time, the system preserves an authenticated session through cookies, tokens, device recognition, or refresh workflows. This is common in streaming, banking, and cloud services where users expect smooth switching between screens.
It matters because it balances convenience with security. Good session continuity reduces friction, but weak implementation can let stolen session cookies or tokens be reused by an attacker, sometimes without a password. Defenders strengthen it with short-lived tokens, secure cookie flags, device binding, reauthentication for sensitive actions, and rapid session revocation when risk changes. In real attacks, session hijacking targets this layer; in defense, monitoring unusual device changes or token reuse helps spot abuse.