Full Answer

Third-party cookies worked by placing an identifier in the visitor's browser that ad networks could read across different websites. Browsers are blocking this. Universal IDs replace the cookie with an identifier derived from data the user consented to share — usually their email address — which is then hashed and encrypted.

Unified ID 2.0, governed by IAB Tech Lab, converts hashed email addresses into pseudonymous tokens that publishers and advertisers can use for targeting and measurement without cookies. LiveRamp's RampID uses deterministic matching (email, phone, address) to link identities across devices and channels. ID5 uses probabilistic modelling from browser signals and first-party data.

For WooCommerce stores, universal IDs are largely an ad platform infrastructure layer managed by The Trade Desk, LiveRamp, and DSPs — not something a store owner configures directly. Their relevance is that they depend on first-party data collection: stores that collect consented email addresses at the point of purchase are best positioned as these frameworks expand.