How ads get sold

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.

Where you'll see it on Ad Spot FinderDSPs & ad exchanges

Related terms

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.
DIRECT vs RESELLEREach line in ads.txt is either the publisher's own account with the exchange (DIRECT) or a third party that may sell the same ad spots too (RESELLER).

All glossary terms