A sign-in flow is the sequence of screens and checks a user goes through to authenticate with a service. It can include entering a username, password, one-time code, passkey, or approving a device prompt. The flow may also involve account selection, single sign-on, and session creation after login succeeds.
In cybersecurity, the sign-in flow is a high-value target because attackers try to intercept, imitate, or weaken it. Phishing pages copy the flow to steal credentials, while malicious prompts can trick users into approving a login they did not start. Defenders study sign-in flows to reduce friction without losing security, adding controls such as multi-factor authentication, risk checks, and clear identity indicators. A well-designed flow helps users understand which account is in control and makes suspicious activity easier to spot.