The most effective way to intercept or modify user data during registration is through the following hooks: Usage Note Runs before the user is saved.
This is the standard approach to identify a vs. an existing user being updated. drupal-8-user-register-hook
Use this for actions that require the new User ID, like sending a custom welcome email or creating related profile entries. Modifies the registration form . The most effective way to intercept or modify
Do you need help on the registration form, or are you looking to redirect users after they sign up? drupal-8-user-register-hook
[Solved] How to hook into Commerce after payment complete - Drupal
Use this to add custom fields or validation logic (e.g., matching a secondary database). 💻 Code Example: hook_user_presave