When you create a custom login page, you need to define a login URL that points to your custom login page. This tells Wix where to redirect users when they encounter Wix-managed business flows that require login, for example a checkout page. If you use a Wix-managed login page instead, this setup isn't required since Wix handles the login process automatically.
Learn more about login options for Headless sites.
To set a login URL:
In your project dashboard, go to Settings > Development & integrations > Headless Settings.
From Headless clients, click the 3 dots to the right of the OAuth app you want to edit. Choose Settings to open the app's settings page:
Scroll down to the URLs section and go to the Login URL section.
Enter the URL to your custom login interface. When Wix needs to log in a member, the member will be redirected to the URL you entered.
Click Save to save your changes and return to Headless Settings.