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Supply layer · position 3 / 8 · SSP
SSP
Supply-side platform — auctions inventory to many DSPs at once.
"The auctioneer working on behalf of the seller (publisher)."
By the numbers
Latency
30–120ms
Take rate
10–20% of media
Common vendors
Magnite · PubMatic · OpenX
In the flow
Where SSP sits
Fun facts
Reshuffle for more — each fact links to its source.
Magnite is what's left after Rubicon Project merged with Telaria in 2020 — the first big SSP roll-up, branded around CTV.
history·Wikipedia
PubMatic processes over 600 billion ad impressions per day — peak QPS rivals the entire global Visa network.
scale·PubMatic
ads.txt was proposed by the IAB in 2017 after a single fake-inventory scheme (Methbot) stole an estimated $5M per day.
failure·IAB Tech Lab
Receives from (upstream)
Sends to (downstream)
Inputs
- · Ad request + user signals
- · Floor price
Outputs
- · OpenRTB bid request to DSPs
- · Winning bid back to publisher
Protocols on the wire
OpenRTB 2.6ads.txtsellers.json
Key KPIs
Bid densityWin rateTake rate
Appears in lifecycle
Featured in scenarios
Under the hood
Magnite, PubMatic, OpenX. Conducts a second-price (or first-price) auction. Enforces floors, applies ad quality scans, and returns the winning creative URL.
Active recall
Test what you know about SSP.