How to disable field on register form but keep show in edit profile?
Drupal 7

In D7 you can edit each user field under Configuration &gt; People &gt; Account Settings &gt; Manage Fields and untick the option Display on user registration form. 

Drupal 8

In D8 after you add your fields under Configuration &gt; People &gt; Account Settings &gt; Manage Fields go to  Configuration &gt; People &gt; Account Settings &gt; Manage form display, scroll down and uncollapse Custom display settings, tick the Register option and Save. 

Now you will see two sub-tabs on that page: Default and Register. Visit the Register sub-tab and rearrange the fields to disable the ones you don't want. This will apply to the Registration form only. 

The Default settings will apply to the User Edit form, so you'll want to keep the field enabled there.