The authentication provider documentation provides a fairly good description for what the 'Existing User Linking URL' does, but I do not understand the context for where and when this URL would be used.

From the docs on creating OpenID connect authorization endpoint, this is the definition:

Use this URL to link existing Salesforce users to a third-party account. The user opens this URL in a browser, signs in to the third party, signs in to Salesforce, and approves the link.

From this description its very clear that this link is meant to be used by existing users in a browser, but how does this work in practice?

From the docs on the registration handler interface, its clear that this URL will only call the updateUser method

This method is called if the user has logged in before with the authorization provider and then logs in again, or if your application is using the Existing User Linking URL

Is the Existing User Linking URL meant to be sent by email to new users after account creation, instead of pointing at the mydomain login page?

Or is it used as the callback URL for the app if you only want the app to match / update existing users? Is there some reason you would go this route of using a specific URL instead of just setting the logic in your registrationHandler.

Specific use cases would be helpful in understanding how this functionality can best be used.

1 Answer 1


"Existing User Linking URL" is used to link a existing portal user to the new Auth Method. It is used when the portal user is already logged in.

User Case:

  1. Exiting user wants to add another authentication method than the current one used
  2. Previous authentication method was revoked. This is to gain the access again

Below is the sample screen for linking existing user to a Facebook account: Link existing user to Facebook

  • Can you elaborate on how this is accomplished. I am using a custom third party app implementing Open Id Connect to implement SSO with a registration handler (NOT FACEBOOK, GOOGLE, etc..). What steps are required in Salesforce / external system to implement existing User Linking logic?
    – Z33dawg
    Mar 22, 2021 at 16:08

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