The lead  ·  01

Safari’s iOS 27 Block Cuts eCPMs 10.5% For Updated Readers. The Sitewide Hit Is About 1%

The first publisher data on Apple’s Safari block shows eCPMs down 10.5% among readers who have updated.

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The week in one paragraph

This was the week the first numbers arrived, and most of them said the measurement is the problem, not the inventory. The first publisher data on Apple’s Safari block put eCPMs down 10.5% among readers who had updated, but only about 8% of Aditude’s Safari users had updated, so the sitewide loss is about 1% today. A buy-side columnist reported one campaign where a DSP pixel counted 109 checkouts and a CRM match found 1,250, and another piece argued that streaming’s 47.6% share of all TV viewing shrinks to a minority of ad-supported viewing, where cable and broadcast still hold 51.8%. Foursquare says it will stay neutral inside Infillion, and buyers and publishers are told to ask for proof. On the institutional side, Prebid’s working group proposed an auction in which ad servers, GAM included, bid into Prebid, and Prebid Summit speakers put addressability back at the top of the agenda. Meta, meanwhile, started selling TV-style reserved windows of 3 to 24 hours around tentpole days, on the same dates publishers sell.