Major
Apple blocks alternative IDs in iOS 27
According to Mobile Dev Memo, iOS 27 activates a WebKit mechanism that unconditionally blocks domains associated with alternative identity providers. The change reportedly affects browsers outside the EU and Japan and could disrupt ad delivery and identity resolution for companies including The Trade Desk.
Why it matters: Marketers and ad-tech teams may need to reassess audience matching, attribution, delivery, and measurement strategies for iOS traffic, particularly where they rely on alternative IDs or deterministic tracking workarounds. The practical consequences could extend beyond one vendor to the wider identity and programmatic ecosystem.

