Let Visitors Sign Up for Your Community by Email or Phone
Where: This feature is available in all communities accessed through Lightning Experience, Salesforce Classic, and all versions of the Salesforce app. Communities are available in Enterprise, Performance, Unlimited, and Developer editions.
Who: External Identity and Communities admins can let visitors register with their email address or phone number. To verify identities via text message, you purchase a license for Identity Verification Credits, which allows your org a predetermined number of SMS messages for identity verification. For exact limits, contact your Salesforce account rep.
How: You set up the self-registration page on the Community Workspaces Login & Registration page. First, select Configurable Self-Reg Page (1). Then choose which fields to display on the sign-up form (2). After you save your registration settings, Salesforce generates the configurable self-registration handler, in this case, AutocreatedConfigSelfReg1532475901849 (3).

The Configurable Self-Reg page generates a sign-up form that prompts users to register with the registration fields that you selected.

You can edit the generated Configurable Self-Reg handler in Apex to further customize self-registration. For example, you can add custom logic to ensure that the email or phone number are unique to the external user. You can modify user creation to eliminate the need for associating contacts with accounts. The handler is located in Setup under Apex Classes. Its name begins with AutocreatedConfigSelf-Reg, such as AutocreatedConfigSelf-Reg1532705701849.