SSPs have been answering fewer ad requests on Safari iOS since Oct. 1, according to early data from French ad monetization platform Hubvisor. Their response rate fell 30%, from 1.84% to 1.30%. Some vendors were hit harder than others. Magnite, Taboola and The Trade Desk saw bid values on iOS fall 32% to 51%, while their numbers on Android held up much better.
What's falling matters more than how much. Ad request volume is flat, at around 1 billion a day. Bid CPMs have barely moved either. SSPs are simply responding less often. Demand isn't losing value. It just can't get through.
"What surprises us isn't the CPMs, since they're stable. It's that some of the SSP responses have vanished. We're seeing as many ad calls as before, but fewer players actually bidding," said Sylvain Travers, CEO of Hubvisor.
The timing is another clue. The break came on Oct. 1, not on Sept. 14, when iOS 27 shipped. That gap fits a blocklist Apple can update remotely, without shipping a new version of iOS.
That lines up with AdExchanger's reporting in early October. The iOS 27 blocklist initially covered The Trade Desk, LiveRamp, ID5, Permutive and Audigent. According to two sources cited by the trade publication, it has since been replaced by a list of hundreds of customer data platforms, ad tech and martech vendors, data sellers and ID graph operators. Apple devices check that list remotely, so it can change without a new iOS release.
Not all of it is on Apple. Android also fell 11% over the period, which points to a broader market effect, partly tied to the start of a new month. Even after accounting for that, iOS still trails by about 20 points. Safari on Mac shows no comparable drop.
Should publishers brace for a revenue collapse? Travers played down the immediate impact. "iOS is about 15% of the total traffic we see. So we're not talking about monetization collapsing across the board. But with an ad market that's already tough for publishers, we could have done without one more piece of bad news."
The lack of alternatives makes it worse. The industry has spent years cutting its reliance on ad identifiers, but semantic targeting doesn't yet look ready to take over at scale.
"There's been a lot of talk about cookie alternatives and new identifiers such as EUID, ID5 or RampID. But once those signals are blocked, semantic targeting isn't effective enough or widespread enough today to make up the loss. You're less able to reach audiences, and that automatically means less demand," Travers said.
Once again, the walled gardens stand to gain. As targeting and monetization shrink on the open web, Google, Amazon and the other big platforms still have their closed environments, first-party data and activation tools.
"Every time we make life a little harder for the open web, we indirectly strengthen Google, Amazon and the walled gardens. Advertisers still need to reach their audiences and measure their campaigns. If that gets harder on the open web, budgets could move to environments where those capabilities are still available," Travers warned.
That may be the real story. Apple doesn't need to ban advertising to reshape its economics. It may only need to stop some ad calls from going through.
On the open web, Apple holds a lot of power over an ad value chain it has no direct commercial stake in. Each new restriction could widen the gap between independent publishers and closed platforms.
