Supply chain · also called intermediary, RESELLER
Reseller
A reseller is a company authorised to sell a publisher's ad inventory through an ad system account that it controls, rather than the publisher's own account, and labelled RESELLER in ads.txt.
In ads.txt terms, every authorised seller is either DIRECT or RESELLER. A reseller line means the account belongs to someone other than the publisher: an ad network, a sales house, a monetisation partner or another intermediary that has the right to sell the inventory and receives payment first.
Resellers can be legitimate and useful. Small publishers rely on networks and management companies that sell on their behalf; some resellers bring demand the publisher could not reach alone. But each resale adds a fee to the ad tech tax, adds hops to the supplyChain object, and multiplies bid duplication.
Resellers are also where problems hide. Unchecked reseller relationships have allowed traffic arbitrage, mixing of low-quality supply into premium-looking paths, and outright fraud. That is why supply path optimization often starts by cutting reseller paths and why buyers check sellers.json to see who the reseller really is.
Think of it like this
A reseller is like an authorised ticket agency: it can legitimately sell your seats, but it adds a fee and you have less control over how the tickets are marketed.
An example
A travel blog's ads.txt has 8 DIRECT and 40 RESELLER lines. After an audit it removes 30 resellers that delivered under 1% of revenue.
Related terms
Direct seller
A direct seller is an ad system account that the publisher itself controls and gets paid through directly, marked DIRECT in the publisher's ads.txt file.
ads.txt
ads.txt (Authorized Digital Sellers) is a public text file on a website's domain listing which ad sellers and accounts are authorised to sell that website's ad inventory.
sellers.json
sellers.json is a public file in which SSPs and exchanges list their seller accounts, naming who owns each one and whether it is a publisher or an intermediary.
Supply path optimization (SPO)
Supply path optimization (SPO) is a buyer's practice of choosing the most direct, cheapest and most trustworthy routes to the same inventory, and cutting unnecessary resellers and duplicate paths.
Traffic arbitrage
Traffic arbitrage is buying cheap visitors, often through native, social or search ads, and sending them to pages loaded with ads that earn more than the traffic cost.