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DOOH GlossaryDSP, SSP & Exchange

SSP (Supply-Side Platform)

A sell-side ad-tech system. Publishers and screen networks expose their inventory through an SSP, which auctions it to DSPs.

A supply-side platform (SSP) is the sell-side counterpart to a DSP. A publisher — or, in DOOH, a screen-network operator — exposes its inventory through one or more SSPs. When a screen requests an ad, the SSP fires a bid request to every DSP it's connected to, holds a unified auction, and returns the winning creative. The SSP takes a percentage fee (typically 10-20%) on the impression revenue before remitting to the publisher.

Major SSPs in 2026 include Magnite, PubMatic, Index Exchange, and FreeWheel (the dominant CTV/DOOH SSP since the Comcast acquisition). On the DOOH side, Vistar Media and Place Exchange are the largest specialists; Magnite and PubMatic each have growing DOOH product lines.

SSP plumbing is governed by two IAB standards. ads.txt declares which SSPs are authorized to sell a publisher's inventory. sellers.json declares the SSP's own list of authorized sellers. Both files are public; both are checked by DSPs before bidding. A missing or stale ads.txt entry is the most common reason a buyer's spend gets stranded.

Trillboards has its own SSP layer (the Adipolo wrapper plus partner exchange connections) — see partner SDK for the supply-side integration spec.

Authoritative reference

IAB Tech Lab — sellers.json

See also

DSP (Demand-Side Platform)
A buy-side ad-tech system. Advertisers (or their agencies) log into a DSP to set targeting, budgets, and creatives — then bid into exchanges.
Ad Exchange
A real-time auction venue that matches DSP buyers with SSP sellers — the marketplace where ad impressions are priced and cleared.
Header Bidding
Pre-auction technique where multiple SSPs bid in parallel before the ad-server call — invented on the web, ported to CTV, now reaching DOOH.
ads.txt / sellers.json
Two IAB transparency standards declaring which SSPs are authorized to sell a publisher's inventory — the spine of supply-side fraud prevention.
sellers.json
An SSP's published list of authorized sellers — pairs with ads.txt to make the full supply path auditable.

Reference docs

Building against Trillboards?

Our developer reference covers the DSP API, partner SDK, proof-of-play verification, and the sensing pipeline that powers buyer-grade audience signals.

View developer docs