The login event
login is a GA4 recommended event that fires when a returning user authenticates into an account. It carries a method parameter naming how they signed in. It measures engagement of existing users and, paired with sign_up, distinguishes new registrations from returning authentications — but it must never record credentials.
What this means
login is a GA4 recommended event fired when a returning user signs in. Its `method` parameter names the authentication option used. GA4 reports it as a standard event, useful for understanding how often your existing users return and authenticate.
It is the recurring counterpart to sign_up: the same person can fire login many times but should fire sign_up only once.
Login as an engagement signal
Login frequency is a proxy for active engagement of registered users. A sudden fall in logins can mean a broken authentication flow, expired sessions, or a cookie/consent change logging people out. Keep login and sign_up distinct so neither metric is inflated. As with all auth events, capture only the method — never credentials, tokens, or session identifiers.
- Fires when a returning user authenticates
- method names the sign-in mechanism
- Recurring counterpart to the one-time sign_up
How it appears in analytics and logs
A login event means an existing user authenticated. A drop in logins among an active base can signal session/cookie problems or friction in the sign-in flow.
Diagnostic use case
Track returning-user authentication to gauge logged-in engagement and compare which sign-in methods people use.
What WebmasterID can help detect
WebmasterID can record login events first-party with the method label, so authenticated engagement is measurable without storing credentials.
Common mistakes
- Counting login as new registrations.
- Recording tokens or credentials in the event.
- Firing login on every page load while a session exists.
Privacy and accuracy notes
login should record that an authentication happened and the method, never the username, password, or token. This is educational, not legal advice.
Related pages
- The sign_up event
sign_up is a GA4 recommended event that fires when a visitor creates an account. It carries a method parameter naming the registration mechanism, such as 'Google', 'email', or 'Apple'. It is a key activation event for products with accounts, marking the move from anonymous visitor to registered user — distinct from logging in, which returning users do repeatedly.
- The session_start event
The session_start event marks the beginning of a visit. In GA4 it is fired automatically the first time a user is active in a new session, and it underpins every session-scoped metric. Understanding when a session begins — and the timeout that ends it — explains why session counts behave the way they do across midnight, campaigns, and idle periods.
- User properties vs event parameters
User properties are attributes that describe a user across all their events — a plan tier, a preferred language, a logged-in state — rather than a single action. They differ from event parameters, which describe one event. Used well, user properties let you segment behaviour by audience. Used badly, they become a place where people stash personal data, which is exactly what they must not hold.
- Events documentation
Track logins first-party.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.