Supply Side Platforms (SSP)

These businesses build and run the systems that sit on the publisher's side of programmatic advertising: the auction infrastructure that takes your ad inventory — a web page, an app screen, a video pre-roll slot — and puts it in front of buyers in real time. Hired directly, they connect your site or app to demand sources (ad exchanges, DSPs, ad networks), run the bidding when a page loads, manage the header bidding wrapper if you're running one, and hand you back a filled ad slot and a payout. What changes for the customer is that inventory which used to sit unsold or get dumped into a single low-paying network now gets bid on by multiple buyers at once, and someone else is doing the technical work of keeping that auction fast, clean and compliant with the ad tech ecosystem's constantly shifting rules.

People go looking for this when their ad revenue doesn't match their traffic. Fill rates are low, CPMs are inconsistent, a direct sales team can only sell a fraction of available impressions, or the site is stuck on one ad network that pays whatever it feels like. Sometimes it's a technical problem: page load times are suffering because of a badly configured header bidding setup, or a mobile app's mediation stack is a patchwork of SDKs nobody fully understands. Sometimes it's growth — a publisher that used direct sales for years now has more inventory than they can sell that way and needs programmatic demand to fill the gap without hiring a sales team to match.

The common approach is the same in outline: connect inventory to demand, run an auction, optimise for yield. Where providers genuinely differ is in the demand pool they bring (a platform with strong video or native demand won't help a display-only publisher much), the formats and inventory types they specialise in — display, native, video, in-app, CTV — and how much they do for you versus how much you self-serve. Some run as close to a managed service, with account managers tuning your setup; others are closer to raw infrastructure you plug into and configure yourself. Worth comparing directly: take rate and how transparent it is, latency added to page load, fraud and brand safety controls, ease of header bidding integration, and how much reporting you actually get on where your money is coming from.