The players
219 companies and organisations that make up ad tech, what each one does in plain English, and where it sits in the chain.
BidSwitch
DivisionPlumbing that connects many DSPs to many SSPs through one integration, owned by Criteo.
Ad exchangesUKGoogle (Alphabet)
GOOGL -0.7%The largest ad business on earth: search ads, YouTube, and tools on both sides of the open-web ad market.
Walled gardens & platformsUSAGoogle Ad Manager
DivisionGoogle's publisher ad server and exchange, the market-leading tool at the centre of the US antitrust case.
Ad serversUSAIndex Exchange
PrivateLarge independent ad exchange and early header-bidding champion, privately owned.
SSPs (sell side)CanadaIPONWEB
AcquiredEngineering firm that built custom ad tech for others (and BidSwitch), acquired by Criteo in 2022.
Ad exchangesUKMicrosoft Advertising
DivisionSearch ads on Bing and Copilot, plus ads across Microsoft properties, Xbox and partner sites.
Walled gardens & platformsUSAOpenX
PrivateLong-running independent SSP and exchange, focused on identity and sustainable supply.
SSPs (sell side)USAXandr (Microsoft Invest/Curate)
DivisionThe former AppNexus exchange, owned by Microsoft, which shut its DSP in 2026 and kept its sell-side tools.
Ad exchangesUSA