External ID

The External ID (refId) is an external alias for a Client ID — an email, phone number, or your own customer ID — that you supply when the Click ID cannot reach a destination such as a CRM.

When to use an External ID

A Click ID travels through links, forms, and integrations. When it can’t (for example, a contact created directly in a CRM, or a destination that only stores your own customer record), you alias the visitor with a refId. Later events identified by that value match back to the same visitor.

External ID vs Client ID

The Client ID is the anonymous cookie AnyTrack sets. The External ID is a value you control and supply. AnyTrack matches a returning conversion back to the original session by the Click ID first, and by the refId when the Click ID could not travel.

Frequently asked questions

FAQ was last reviewed on 2026-06-23

When should I use refId instead of the click_id?

Use refId when the click_id cannot be passed to a destination such as a CRM. It aliases the visitor by an external value you control, like an email or your own customer ID, so later events identified by that value match back to the same visitor.