Signin

Sign-in refers to the process by which a user proves their identity to access a secure system, service, or resource. It typically follows account creation (sign-up) and is distinct from temporary or anonymous access. Credentials used vary, but commonly include a username or email and a secret such as a password.

Authentication methods include traditional username and password, multi-factor authentication, biometrics, hardware security keys (FIDO2/WebAuthn), and magic links or one-time codes. Some systems support single sign-on (SSO) through a trusted identity provider to access multiple applications with a single authentication event.

In the usual flow, the user submits credentials on a sign-in form; the server verifies them and, if valid, issues a session token or cookie to maintain authentication across requests. Security measures include enforcing encrypted connections (HTTPS), salting and hashing stored passwords, MFA, rate limiting, and account lockout or anomaly detection.

The user experience should prioritize clarity, accessibility, and recoverability. Sign-in forms should be accessible via different input methods, support keyboard navigation, and provide options for password reset or account recovery while minimizing phishing risk.

Common issues include forgotten passwords, phishing, and credential stuffing. Best practices encourage the use of unique passwords, enabling MFA, and leveraging password managers. Related terms include authentication, sign-out, and sign-up.