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WebKit: Privacy Preserving Ad Click Attribution for the Web

John Wilander, WebKit engineer at Apple:

The combination of third-party web tracking and ad campaign measurement has led many to conflate web privacy with a web free of advertisements. We think that’s a misunderstanding. Online ads and measurement of their effectiveness do not require Site A, where you clicked an ad, to learn that you purchased something on Site B. The only data needed for measurement is that someone who clicked an ad on Site A made a purchase on Site B.

Today we are presenting a new technology to allow attribution of ad clicks on the web while preserving user privacy.

This is an amazing proposal, and I really hope it takes off. Safari’s incredible popularity and importance on mobile devices could make this take off. The key idea is this: a web browser should work in the interest of its users.

Critically, our solution avoids placing trust in any of the parties involved — the ad network, the merchant, or any other intermediaries — and dramatically limits the entropy of data passed between them to prevent communication of a tracking identifier.

Anything that relies on voluntary compliance is doomed. If it can be abused or circumvented, ad networks and other web trackers will abuse or circumvent it.

See also: Zack Whittaker’s story at TechCrunch, and this brief thread from Apple’s Maciej Stachowiak with links to other WebKit privacy initiatives.

Wednesday, 22 May 2019