Safari is cutting off the ID vendors

With the iOS 27 rollout in September, Safari began restricting identity providers, including The Trade Desk and LiveRamp, according to EMARKETER. Apple is reportedly building a larger list of hundreds of ad tech vendors that it can update at any time, without waiting for a new iOS release. Safari carries 15.7% of global web traffic, per StatCounter, and is the default browser on every iPhone and iPad. For many brands, that is too large a share of customers to treat as a blind spot.

What Apple changed

On October 19, Apple's WebKit engineers explained the policy in a post titled "Blocking Identity Resolution Infrastructure." Safari now blocks network access to companies that turn an email address collected at login or sign-up into a persistent ID used across sites. The blocking happens at the domain level, so vendors cannot get around it by changing how their requests are built. It ships in the iOS, iPadOS, macOS and visionOS 27 releases.

Apple also drew a line worth noting. The post says, "First party personalization is not tracking, and is not what our technologies seek to prevent." In other words, what a brand does with data from its own customers, on its own properties, is not the target. What is at risk is the third-party layer that links people across sites and devices.

Why measurement feels it first

Cross-channel measurement often depends on one ID vendor to connect an ad exposure on one site to a visit or sale somewhere else. When Safari blocks that vendor, the link breaks for Apple users, and reports can show fewer conversions without any real change in results. Spend may then shift away from channels that are still working.

The early data shows the effect is real but still building. Digiday reported on October 12 that, for publisher ad platform Aditude, eCPMs fell 10.5% among Safari readers on the new update, while only about 8% of users had upgraded so far. As more people update, the gap will widen. Publishers lose revenue too, which can affect the inventory and reporting brands get from them.

Four things to consider

1. Map where IDs sit today

List every tool in your measurement chain that relies on a third-party ID to connect users across sites. Include attribution, audience building and frequency controls. You cannot plan for gaps you have not found.

2. Strengthen first-party data

Customer accounts, email sign-ups, loyalty programs and your own site analytics are not the target of Apple's change. Collect this data with clear consent and give people a reason to share it. It becomes the base that every other method can build on.

3. Use tests you control

Holdout tests, geographic tests and before-and-after comparisons measure lift without following individuals across sites. They take more planning but hold up when IDs disappear. Run at least one on a major channel this quarter.

4. Ask partners for specifics

Ask each ad tech and measurement partner whether it is affected and what its plan is for Safari users. Ask how they will report the share of conversions they can no longer see. A clear, documented answer is worth more than reassurance.

Build for more than one ID

Apple has not published its list, and it can change at any time. That makes any single ID vendor a fragile foundation for measurement. The stronger position is a plan that combines first-party data, controlled tests and partner reporting, so no one blocked domain can take your view of performance with it. We help brands build that kind of plan and weigh partners against it.

Questions to ask your team

• Which of our reports depend on a third-party ID?

• What share of our customers use Safari?

• Have our partners told us how they are affected?

• Which channel could we test with a holdout first?