Apple's Safari block pushes ad tech server-side, WPP pitches InfoSum
Ad tech firms like ID5 are moving identity work onto publisher servers, while WPP argues its data business barely feels the change.
Apple’s latest Safari block is pushing ad tech to move identity work off the browser. If your ads or attribution rely on email-based identity matching, your Safari numbers deserve a second look.
What Apple blocked
Apple has started blocking some identity resolution firms in Safari, and Digiday’s WPP report explains why.
Identity resolution runs on email.
When you sign in, a small script scrambles your address. It sends the result to a firm, which returns an ID it can match across sites.
In an October 19 blog post, Apple’s engineers argued the firm in the middle sees the same email from every site. That lets it connect one person’s activity across them.
Apple’s explanation came after the restrictions took effect.
Live tests that week, reported by Digiday, included:
- Audigent
- ID5
- LiveRamp
- Permutive
- The Trade Desk
Where ad tech is heading
ID5 is preparing to move more of its identity work to the server.
Its CEO, Mathieu Roche, says the device is powerless to block that. That matters if you run a publisher site.
Roche admits it’ll be harder for smaller publishers, especially those that outsource their ad operations. He says larger ones could finish the work in days rather than months.
Who on your team would run a setup like that?
If you outsource your ad operations, ask your provider whether and when they’d make this move.
IAB Tech Lab’s Trusted Server Framework, introduced in March 2025, proposes moving ad requests and auctions onto publisher-run servers.
Critics raise concerns about:
- complexity
- cloud dependence
- fingerprinting
Some industry sources doubt server-side fixes the root problem. Moving identity matching off the device could just put it beyond Apple’s browser controls.
WPP’s pitch for InfoSum
On WPP’s third-quarter earnings call, CEO Cindy Rose said the block doesn’t really affect its data solution.
Her argument: WPP relies on more than identity matching, and it bought InfoSum about two years ago.
InfoSum keeps each party’s data in its own sealed environment. It shares only the insights, which keeps it away from the browser and outside what Safari blocks now.
Robert Webster, a former WPP executive, says the company has taken some damage.
He argues many of the ad tech systems WPP uses are just as hampered by Apple’s policies. He also says Publicis has a well-known match-rate advantage.
Publicis agreed to pay $2.2 billion for LiveRamp in May. LiveRamp is now on Apple’s blocklist.
Winterberry’s Charles Ping read Rose’s comments as a message aimed at that deal.
Why it matters
My read: the sources don’t put a number on how much attribution will drop. Nobody’s got that number yet.
But if your Safari reporting depends on a third-party email match, I’d expect it to get thinner over time.
Which tools on your site pass email addresses to a third party? Start with the scripts that run at sign-up or checkout, and ask your developer what each one sends.
After that, I’d put server-side events from your own checkout or CRM first. They also mean infrastructure you have to build and maintain.
Does your Safari conversion count still match what your CRM shows?
If the gap keeps widening, you’ll see it in your own numbers before any industry headline does. Let those numbers decide before you rebuild anything.
Permutive says only a small number of its customers were affected. Several sources say low iOS 27 adoption has created far more discussion than measurable disruption.
Of course, the next restriction could hit another part of your stack. I’d expect more of them, and I’d rather you hear about them from your own reports first.
Common Questions
Does Apple’s Safari block stop all tracking?
The sources describe a block on identity resolution firms, which match email addresses across sites. Digiday’s reporting doesn’t say the block covers every form of tracking.
What is server-side tracking in this context?
It means the identity or ad function runs on the publisher’s own servers instead of the visitor’s browser. IAB Tech Lab’s Trusted Server Framework is one proposal for doing that.
Is WPP’s InfoSum affected by Apple’s block?
WPP says the block doesn’t really affect its data solution, and the sources describe InfoSum as working away from the browser. Robert Webster, a former WPP executive, argues the company isn’t unscathed.
