Auth0 and Ionic v3 user registration

I have 2 ionic apps, one with IOS and one with Android. I like to know if I can customise the user signup process ? I’d like to add additional fields like DOB etc. Is it possible to do this in Auth0? Can I store the data in my own API?

If you refer to the signup of user with username/password credentials, more specifically, users that will be associated with a database connection then the signup endpoint allows you to pass additional information that will be stored as part of user_metadata. If you choose this route and are using an SDK/library you should check the docs to see how/if the library exposes that functionality.

You could also store it as part of your own storage and making the link of which data belongs to which user by the means of a unique value. This could be the Auth0 user identifier or even an email.