What is identity linking, and what are everyday examples of it?

Identity linking connects several digital identities of the same user so that they can be used alternatively; examples are Zoom linked to an HSLU account, Digitec or Galaxus linked to a Google, Meta or Apple account, and HSLU linked to the Switch edu-ID.

In the information model this is a self-association: a digital identity may reference any number of linked identities (linkedID). Practically it means a relying party keeps its own user record but accepts a login through another identity, or a person's accounts at two organisations are tied together.

The examples show the two typical situations:

• Social or institutional login: the shop (Digitec) keeps its customer identity but lets you authenticate with Google, Meta or Apple. The two identities are linked; either can be used.
• Institutional federation: an HSLU account is linked to a Switch edu-ID, so that one edu-ID login opens HSLU services.

Linking is convenient but makes the linked identities depend on each other: if the Google account is lost or blocked, the shop login it was linked to is affected too.

Go deeper:

• Social login (Wikipedia) — identity linking in its most common form, with its convenience and privacy trade-offs.