Login & Sign Up

login and sign_up are GA4 recommended events. Implementing them correctly gives you authentication funnel data — how many users register vs. sign in, which authentication methods are most popular, and where in the funnel authenticated users convert differently from anonymous users.

More importantly, login is the event where you should set user_id — GA4’s mechanism for cross-device and cross-session user identification.

login event

When to fire

Fire login after a successful authentication — after the server confirms the credentials are valid and the session is established. Not on form submission, not on button click — after success.

// After successful authentication response
dataLayer.push({
  event: 'login',
  method: 'email',         // how the user authenticated
  user_id: '12345'         // hashed or anonymized user identifier
});

Login with user properties

The login event is your opportunity to push user properties to GA4 — attributes that should persist across the user’s session and inform your audience segmentation.

dataLayer.push({
  event: 'login',
  method: 'google',
  user_id: 'hashed_user_42813',

  // User properties — these persist in GA4 as user-scoped dimensions
  user_type: 'returning_customer',
  user_loyalty_tier: 'gold',
  account_created_year: '2022',
  has_active_subscription: true
});

Event schema

Event Schema login

Parameter	Type	Required	Description
event	string	Required	Must be "login"
method	string	Optional	Authentication method. Recommended values: email, google, facebook, apple, sso.
user_id	string	Optional	Hashed user identifier. Never use PII. Must be consistent across sessions and devices.

sign_up event

When to fire

Fire sign_up after a successful account creation — when the new account has been confirmed on the server, not when the user clicks Submit.

// After successful account creation
dataLayer.push({
  event: 'sign_up',
  method: 'email',         // registration method
  user_id: 'hashed_user_new_98765'
});

sign_up with registration context

dataLayer.push({
  event: 'sign_up',
  method: 'email',
  user_id: 'hashed_user_new_98765',

  // Optional: registration context
  referral_source: 'friend_invite',
  newsletter_opted_in: true,
  account_type: 'personal'
});

Event schema

Event Schema sign_up

Parameter	Type	Required	Description
event	string	Required	Must be "sign_up"
method	string	Optional	Registration method. Recommended values: email, google, facebook, apple.
user_id	string	Optional	Hashed identifier for the newly created user.

Setting user_id in GA4

The user_id parameter on login and sign_up is special in GA4. When you configure a GA4 Event tag in GTM to send a user_id parameter, GA4 uses it to stitch together sessions and events across devices.

For GA4 to actually receive and use the user_id, you need to configure the GA4 Configuration tag (or Google Tag) to read it. Add a user_id parameter to the configuration tag that reads from a Data Layer Variable — not just as an event parameter on the login event.

// GTM Data Layer Variable: DLV - user_id
// Path: user_id

// This variable should be read by the GA4 Configuration tag's "user_id" field
// as well as included in the login/sign_up event parameters

Caution

Never push actual user IDs, email addresses, names, or any PII to the dataLayer. The user_id you push must be a server-generated hash or pseudonymous identifier — not a value that could be used to identify an individual. Check your privacy policy and applicable regulations (GDPR, CCPA) before implementing user identification tracking.

Recommended method values

Use consistent, lowercase values for the method parameter:

// Standard authentication methods
method: 'email'
method: 'google'
method: 'facebook'
method: 'apple'
method: 'twitter'
method: 'microsoft'
method: 'sso'          // enterprise SSO
method: 'magic_link'   // passwordless link
method: 'phone'        // SMS/phone verification

GTM configuration

Both events follow the same pattern:

1. Create a Custom Event trigger for login and another for sign_up.
2. Create a Data Layer Variable for method and user_id.
3. Create GA4 Event tags for each event, mapping method and user_id as event parameters.
4. In your GA4 Configuration tag, also map user_id to the GA4 user_id field.

Common mistakes

Pushing PII. Never push email addresses, names, or readable user IDs. Use a server-generated hash.

Firing on form submission instead of success. If authentication fails (wrong password), the event should not fire. Fire only after server confirmation.

Not setting user_id on login. If a user signs in and you don’t push their user_id, you lose the cross-session stitching that makes user-level analysis possible in GA4. Login is the moment to set it.

Different user_id formats between devices. The user_id must be the same string across all devices and sessions for the same user. If your web app generates user_42813 but your mobile app generates 42813, they won’t stitch in GA4.

Form Submission Form event tracking — including login and registration form interactions.

Error Events Tracking authentication failures and validation errors.

Custom Event Design How to design custom events when GA4 recommended events don't fit.