What is Ad Exchange?
An ad exchange is a digital marketplace that runs automated auctions for ad impressions, receiving inventory from publishers or SSPs and passing bid requests to buyers, usually through demand-side platforms, then selecting the winning bid.
Also known as: Exchange, Programmatic exchange
How it works
An ad exchange sits in the middle of a programmatic trade. On one side are sellers: publishers, app developers, CTV services and the supply-side platforms (SSPs) that represent them technically. On the other side are buyers, usually connected through demand-side platforms (DSPs).
When an impression becomes available, the exchange receives it and sends bid requests to connected buyers, typically in the OpenRTB format. Buyers respond with bids. The exchange applies the auction rules, such as floor prices, deal priorities and whether the auction is first or second price, and returns the winner. The whole process is a real-time bidding auction that completes in milliseconds.
Exchanges usually support several trading types: the open auction, private marketplaces for invited buyers, and fixed-price deals such as programmatic guaranteed. They also apply policies, for example blocking certain ad categories or filtering suspected invalid traffic.
Why it matters
Exchanges made it practical for thousands of buyers and sellers to trade individual impressions without signing separate agreements with each other. That opened programmatic demand to publishers of all sizes and gave buyers scale across many sites and apps.
The same openness creates challenges. The same impression may be offered through several exchanges and resellers, so buyers can end up bidding against themselves or paying extra fees along longer paths. Industry tools such as sellers.json, ads.txt and the SupplyChain object help buyers see who is selling what, and supply path optimization helps them choose cleaner routes. For publishers, this means it pays to be clear and consistent about which exchanges are authorised to sell their inventory.
Example
Illustrative example. A regional news publisher works with two SSPs, each of which runs or connects to an exchange. When a reader opens a story, both send the impression into their auctions. A sports brand's DSP, connected to both, sees the same impression twice. Its supply path settings tell it to bid only through the path with a direct relationship to the publisher, so it ignores the second request and bids once.
IncrementX perspective
IncrementX should not be thought of as only an ad exchange. It is a media representation partner that helps publishers and media owners connect their inventory with advertiser demand, using technology and demand relationships to support that work. Exchanges and other programmatic channels are part of how represented inventory reaches buyers, alongside direct demand, curated deals, PMP and PG. Through the Demand Marketplace and Media Representation, the focus is on presenting inventory clearly so the right buyers can find and value it.