login

Login is the process by which a user proves their identity to a computer system or online service in order to access personalized resources. The goal is to verify identity while preventing unauthorized access and enabling a tailored user experience.

During login, a user typically provides credentials, such as a username or email and a secret credential like a password. The service checks the credential against stored data, commonly by comparing a cryptographic hash rather than the plain password. If the credential is valid, the system creates a session and issues an authentication token or cookie to preserve the user's authenticated state for subsequent requests.

Common login methods include password-based authentication, multi-factor authentication (MFA) such as codes from an authenticator app, biometrics like fingerprint or facial recognition, and hardware tokens. Some systems also use passwordless options, for example magic links or hardware keys.

Security considerations include using MFA, avoiding password reuse, using a password manager, and ensuring transport encryption via TLS. Systems should implement protections against phishing, credential stuffing, and brute-force attacks, such as rate limiting and account lockouts. Proper session management, secure storage of credentials, and regular audits are also important.

Related concepts include single sign-on and federated identity, which allow users to authenticate across multiple services using a single identity provider. Passwordless login, using cryptographic keys or trusted devices, is a growing trend.

User experience and accessibility considerations include clear error messages, mechanisms for account recovery, and support for assistive technologies. Providers may offer reminders and security prompts to help users recognize unusual login activity.