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When trackers share IDs so they can recognize you together.

Definition

Cookie syncing is when tracking companies share or match their cookie IDs for the same person.

In plain English When trackers share IDs so they can recognize you together.

Why this matters

Why it matters: It spreads your identifier across more companies, making tracking harder to avoid.

Example

Example: Two ad companies “sync” so both know the same browser belongs to one user.