How can a buyer check that a CTV deal is authorised by the publisher?

A buyer can check whether a CTV deal is authorised by comparing two things: the seller that actually sold each impression, and the sellers the app's publisher has declared as allowed to sell it. If the seller appears in the publisher's own declaration, the route is authorised. If it doesn't, it isn't. If the declaration can't be found or read, nobody can say either way.

Where the publisher's declaration lives

For websites, publishers list their authorised sellers in an ads.txt file on their own domain. For mobile and CTV apps, the equivalent is app-ads.txt, hosted on the developer's website that the app store listing points to. Each line names an ad system, the seller's account ID, and whether that seller is direct or a reseller.

Where the seller's identity comes from

Every impression in a buyer's delivery data carries the SSP and the seller account that sold it. The SSP's own sellers.json file then says which business is behind that account. Put the two files together and you can see both sides of the route: who the publisher allowed, and who was actually paid.

• Identify the app behind each impression, usually from its bundle ID
• Find the app's app-ads.txt through its app store listing
• Match the seller account on each impression against that file
• Use the SSP's sellers.json to confirm who that seller really is

Why so much CTV still can't be confirmed

In practice, a large share of CTV fails at the very first step. Bundle IDs don't always map cleanly to an app store listing, and many CTV apps and channels publish thin or missing declarations. When that happens, there's nothing to check the seller against.