How ad IDs can survive a deleteSourced
Ad companies can match their user IDs.
Some tracking can resist deletion.
Cookie syncing lets advertising parties connect separate identifiers for the same browser. Research notes that pairing it with persistent cookies or fingerprinting can create systems designed to resist user deletion. This describes a possible method, not every website.
A cleared cookie
may not clear every link.
Summary / translation: Unbubly · CC BY-SA 4.0
Source and reuse details
Cookie syncing · Wikimedia contributors
Adapted, summarized and translated from the source. Adapted text is also available under CC BY-SA 4.0.
Reviewed: 2026-10-01