An SSP (supply-side platform) is the publisher-side interface to programmatic advertising. Publishers use SSPs to: route their ad inventory to ad exchanges, set floor prices, manage which demand partners can bid, block specific advertiser categories, and report on eCPM and fill rate. The SSP handles the programmatic plumbing — ad exchange integration, bid request routing, response aggregation — so publishers focus on inventory strategy.
Major SSPs in 2026
- Magnite — largest independent SSP. Formed from the 2020 merger of Rubicon Project and Telaria; further expanded with SpotX. Strong in CTV and broader programmatic.
- PubMatic — large independent SSP, publicly traded. Strong in mobile and emerging-market inventory.
- OpenX — independent SSP focused on premium publisher relationships.
- AppLovin Exchange (ALX) — AppLovin's SSP layer, integrated tightly with AppLovin's mediation stack.
- Google Ad Manager (formerly DFP + AdX) — Google's SSP for publishers using Ad Manager.
- Index Exchange — independent SSP, strong in header bidding.
- Smaato — mobile-app-focused SSP.
- Verve (formerly Smaato + others) — consolidated mobile-app SSP.
Most large mobile-app publishers integrate 3-8 SSPs into their mediation stack to maximize bid competition.
SSP vs ad exchange — easy to confuse
- SSP: publisher-facing platform. The publisher configures their inventory, floor prices, demand allowlists / blocklists in the SSP UI.
- Ad exchange: the auction venue itself — the place where DSPs bid on inventory routed by SSPs. Some platforms blur the line (Magnite, PubMatic, OpenX have both SSP and exchange functions).
In practice, most modern programmatic players combine SSP + exchange functions into a single integrated platform — the distinction matters more in legacy systems than in 2026 architecture.
What publishers configure in an SSP
- Inventory definition: which ad slots / formats / pages are being made available.
- Floor prices: minimum bid below which the slot won't sell. Critical lever — too low = cheap inventory, too high = unfilled slots.
- Demand partner management: which DSPs / advertisers can bid (allowlists / blocklists).
- Brand safety: which advertiser categories to block (competitors, sensitive categories).
- Frequency capping: max impressions per user per advertiser.
- Header bidding configuration: which SSPs / exchanges participate in pre-bidding (for unified auctions).
SSP role in mobile app mediation: most mobile-app publishers use a mediation platform (AppLovin MAX, ironSource LevelPlay, Google Admob Bidding) that aggregates SSPs + direct SAN integrations + in-app exchanges into a single waterfall or real-time auction. The mediation platform sits above SSPs and orchestrates demand. SSPs are still important — they're how the publisher accesses open-exchange programmatic demand beyond direct SAN deals.