Channels & programmatic
Ad exchange
An ad exchange is the marketplace where programmatic auctions happen: DSPs bid on behalf of buyers, SSPs offer inventory on behalf of publishers, and the exchange resolves the auction in real time, typically in under a hundred milliseconds before the page finishes loading.
In practice
Exchanges are infrastructure rather than a planning decision, but understanding the auction explains programmatic pricing behaviour: competition, timing and signals move CPMs continuously.
Open-exchange buying offers maximum scale with the least control; deal-based buying trades some scale for known inventory.