loggingin

Logging in, or signing in, is the process by which a user proves their identity to an information system in order to obtain access to protected resources. It typically involves presenting credentials such as a username and a secret, usually a password. Modern systems often supplement this with multi-factor authentication, biometrics, hardware tokens, or push-based approvals to increase security.

Most login flows involve a client sending credentials to an authentication service over a secure connection. If the credentials are valid, the server issues a session identifier or an access token that the client uses to authenticate subsequent requests. Sessions may be tracked with cookies, tokens, or device-bound credentials, depending on the architecture. Some systems employ single sign-on or federated authentication, allowing users to log in once to access multiple services.

Security considerations include using strong, unique passwords; enabling MFA; avoiding phishing and credential reuse; ensuring transport security with TLS; and managing sessions to prevent hijacking. Passwords should be stored by servers as salted hashes. Users are advised to use password managers and to monitor for unusual login activity.

Common issues include forgotten passwords, account lockouts after failed attempts, and problems with two-factor devices or codes. Users may encounter noisy error messages or accessibility barriers if the login interface is poorly designed.

Variants of login include device-local access (PINs), biometrics, hardware security keys (such as FIDO2), and social or enterprise single sign-on. The login process is a central component of access control and user accountability in information systems.