How ads get sold

Header bidding

A publisher offers each impression to several SSPs at once, and its ad server picks the winner. That's why one site can sell on many exchanges.

Where you'll see it on Ad Spot FinderExchanges card, on every publisher page

Related terms

Demand-side platform (DSP)Software you use to buy ads programmatically. One login gives you access to many exchanges, and it's the only part of programmatic a buyer signs in to.
Supply-side platform (SSP)The publisher's side of programmatic. It puts ad spots up for auction and takes bids from DSPs. You never log in to one, but you can switch it on inside your DSP.
Ad exchangeThe marketplace where publishers' ad spots are auctioned to DSPs in real time. Most SSPs run their own, so people often use the two words for the same thing.
Sales house (intermediary)A company that sells a publisher's ad spots programmatically under its own accounts, like Freestar, Mediavine or Playwire. It's who you agree a deal with.
ads.txtA public file where a publisher lists which exchanges and accounts may sell its ad spots.
sellers.jsonA file each exchange publishes that says who is behind each account ID, and whether it's the publisher or an intermediary.

All glossary terms