DSP vs SSP, explained for the people selling the ad space

DSP vs SSP comes down to who each platform works for. A demand-side platform (DSP) is the advertiser's tool for buying ad impressions. A supply-side platform (SSP) is the publisher's tool for selling them. They meet in an automated auction every time your page loads.

Here's why it matters to you. Most guides on DSP vs SSP are written by companies selling a DSP, so they explain everything from the buyer's chair. But you're the seller. You'll never log in to a DSP, yet DSPs decide what your ad space is worth, and some of them skip your site for reasons you can fix.

This guide covers both platforms from your side: what each one does, how they meet in one auction, where the fees go and what DSPs check before they bid.

What is a DSP?

A DSP, or demand-side platform, is software that advertisers and agencies use to buy ad impressions automatically across many websites and apps. It decides, one impression at a time, whether to bid and how much. That's the short way to define DSP.

The advertiser sets up a campaign in the DSP: the budget, the audience, the countries, the ad sizes and the most they'll pay. Then the DSP listens for bid requests from exchanges and SSPs. When an impression on your page matches a campaign, the DSP sends a price. When it doesn't, the DSP passes.

A good example is Google's Display & Video 360. Google's Display & Video 360 page says buyers can "bid on or exclude impressions from dozens of third-party exchanges." That's exactly what a demand side platform does.

What a DSP looks at before it bids

A DSP judges each impression on what it can see in the bid request and what it already knows about your site:

• The page URL, the ad size and where the slot sits on the page.
• The device, browser, country and time of day.
• Any audience data the visitor has consented to share.
• Your site's track record: viewability, invalid traffic and how often its ads got clicked or watched.
• Whether the seller is authorised, through your ads.txt and the SSP's sellers.json.

Most of that list is about your site, not the ad. That's the point publishers miss. The audience part is yours to shape too, and our DMP guide for publishers explains how segments reach the bid request.

What is an SSP?

An SSP, or supply-side platform, is software that sells a publisher's ad impressions to many buyers at once. It packages each impression, sends it out as a bid request, collects the bids and passes the best one to your ad server.

The SSP works for you. It's where you set the rules for selling: price floors, blocked advertisers or categories, which buyers can join private deals and which ad formats you allow. Each SSP also brings its own set of buyers, so two SSPs rarely return the same bids for the same impression.

Today the line between an SSP and an ad exchange is blurry. Most SSPs run their own exchange, and Google AdX works as both the exchange and the sell-side auction inside Google Ad Manager. For how AdX compares with the simpler option, see our AdX vs AdSense guide.

DSP vs SSP side by side

The difference between DSP and SSP is the side of the trade. The DSP spends the advertiser's money and wants the best impression for the lowest price. The SSP sells your impressions and wants the highest price for each one. Same auction, opposite goals.

One way to remember it: demand is the money coming in, supply is your ad space going out. DSP vs SSP is buyer vs seller.

How DSP and SSP work together in one auction

DSPs and SSPs work together through a shared bidding language, in an auction that runs while your page loads. Your SSP offers the impression, the DSPs bid, and your ad server picks the winner under your rules.

That shared language is mostly OpenRTB. IAB Tech Lab's OpenRTB page calls it "an open protocol for the automated trading of digital media," which lets buy side and sell side "transact RTB at scale." Here's one impression, step by step:

1. A reader opens your page. The ad code in each slot asks for an ad.
2. Your SSPs get the request. With header bidding, several SSPs get it at the same time.
3. Each SSP sends a bid request. It goes to the DSPs and exchanges it's connected to, with the page, slot, device and country.
4. The DSPs bid or pass. Each one checks the impression against its campaigns and replies in milliseconds.
5. Each SSP returns its best bid. Bids under your floor in that SSP are dropped.
6. Your ad server picks the winner. It compares the SSP bids with AdX and any deals, then serves the winning ad.

First price, not second price

Google Ad Manager runs a first-price auction. Google announced it was moving to unified first price auctions in 2019, and its auction model page says "Ad Manager determines the winning bidder based on the highest net bid submitted." It adds that "the winning buyer is never charged more than the bid it submits."

Some older DSP vs SSP articles still say the winner pays the second-highest price. That was true years ago. Don't set your floors around it today.

Where header bidding fits

Header bidding is how you get several SSPs, and so many more DSPs, into the same auction. Prebid's introduction says its bid adapters "communicate with the bidders (SSPs, DSPs, and exchanges)." Google's own server-side option, Open Bidding, lets you "invite third-party SSPs (supply-side platforms) to compete for your inventory in a single auction in real time." Our guide to programmatic advertising for publishers covers both in more depth, and our walkthrough on setting up Prebid.js with Google Ad Manager shows how to put more SSPs on your pages.

DSP and SSP examples

The best-known DSPs and SSPs are big ad-tech platforms, and many companies run more than one piece of the chain. Here are common DSP and SSP examples you'll see in reports and pitches. This isn't a ranking.

Can one company run both? Yes, and it's common. That's why it's worth reading each partner's terms to see which side they're working for in your deal.

Where to see them in your own setup: open your Ad Manager reports and add the buyer or advertiser dimensions. You'll find the DSPs buying your inventory there, even though you never signed anything with them.

Who pays which fee between DSP and SSP

The advertiser pays the DSP, and you pay the SSP. Each takes its share from the same dollar on its way to you, which is why the price a brand pays is never what you receive.

Here's a made-up example with round numbers to show the shape. Real fees vary by platform, deal and contract, so check your own.

In that example, the brand thinks it paid $4.00 for 1,000 views. You see a $2.20 eCPM. Both are right; they're measured at different points. Our eCPM guide shows how to work out your own numbers.

You can't see the DSP's fee. You can see the SSP's. Most SSP dashboards show gross and net revenue, and a partner's contract states its share. When we compare partners for a publisher, we look at net revenue per thousand page views, never the headline CPM.

Why DSPs skip some sites, and how to fix it

DSPs skip sites they can't verify, can't see clearly or don't trust. Most of the reasons are fixable from your side, and fixing them usually does more than adding another SSP. This is the order we check when we review a site.

1. Your ads.txt doesn't list the seller

Buyers check that each SSP is authorised to sell your inventory. IAB Tech Lab says ads.txt lets publishers "publicly declare the companies they authorize to sell their digital inventory." A missing or wrong line means many DSPs won't bid at all. Our ads.txt guide for publishers walks through the file line by line.

2. The sellers.json entry doesn't match

DSPs also read each SSP's sellers.json. IAB Tech Lab says sellers.json lets buyers "discover who the entities are that are either direct sellers of or intermediaries in the selling of digital advertising." If your seller ID there doesn't match your ads.txt, the path looks shaky. See our sellers.json explainer for how to check yours.

3. No consent signal where it's needed

In the UK and EU, a missing or broken consent signal means many buyers can't use audience data, so they bid low or not at all. Make sure your consent tool sends a valid signal to every SSP.

4. Slow pages and low viewability

DSPs price in the chance an ad is actually seen. Ads that load late, sit far below the fold or shift the layout get lower bids over time. Reserve space for each slot and load ads near where people read.

5. Too many intermediaries

Every reseller in the chain adds a fee and a hop. Many buyers prefer the shortest, most direct path to your inventory. If the same SSP appears through three resellers in your ads.txt, trim it.

6. Floors set too high

A floor that's above what most DSPs will pay just drops bids. In Ad Manager, pricing rules let you "centralize the management of auction floor prices for your non-guaranteed demand." Start lower, then raise floors by country and device while you watch fill rate.

Do publishers need a DSP?

No. Publishers don't need a DSP. A DSP is a buying tool, and you're selling. What you need is a way for as many DSPs as possible to reach your impressions, which means an ad server plus one or more SSPs or exchanges.

Where it gets confusing is when a sales pitch says a partner "connects you to top DSPs." Every SSP does that. The useful questions are different:

• Which DSPs actually buy through this SSP in your main countries?
• Does it support the formats you sell, like video or native?
• Is it a direct seller in your ads.txt, or a reseller?
• What share does it keep, and do you see gross and net in the reports?
• Does it add page weight, or run server-side?

Our take: three to five good demand sources, with clean files and sensible floors, beat a dozen partners on a slow page. That's where most of the gain is.

Private deals with specific DSPs

Once a buyer asks for your inventory, you can sell to that buyer's DSP directly through a deal. Google's Private Auctions overview says they let you control the sale of non-guaranteed inventory "by inviting specific buyers to bid at set minimum floor prices." Google's Programmatic Guaranteed vs Preferred Deals page explains the fixed-price options. These still run from your SSP or ad server. You never need a DSP account of your own.

How to get more DSPs bidding on your inventory

You get more DSPs bidding by widening the paths to your inventory and making each one easy to trust. Work through this list in order; each step builds on the one before it.

1. Fix ads.txt so every seller you use is listed once, with the right seller ID and relationship.
2. Check each partner's sellers.json entry matches your ads.txt line.
3. Set up a consent tool that passes a valid signal to every SSP, in every region you get traffic from.
4. Move from a single network to an ad server, so more than one source competes for each impression.
5. Add header bidding or Open Bidding with a few strong SSPs, and set a bidder timeout.
6. Reserve space for ad slots and keep them close to the content people read.
7. Start floors low, then raise them by country and device as you watch fill rate.
8. Look at which DSPs buy most in your reports, and offer private deals to those buyers once you have a clear audience.

Step 4 is the big one for most AdSense sites. Until an ad server is in charge, you can't add SSPs, so most DSPs only reach you through one door. Our guide to getting Google AdX access explains how publishers usually make that move.

Does the cookie news change any of this?

Not much for now. In October 2025 Google said Chrome will keep its current approach to third-party cookie choice and retire several Privacy Sandbox tools. DSPs still value consented first-party data and clear context, so good consent and a well-structured site keep paying off either way.

Frequently asked questions

What is the difference between DSP and SSP in simple terms?

A DSP buys ads for advertisers and an SSP sells ad space for publishers. They meet in the same automated auction. The DSP wants a low price for a good impression, and the SSP wants the highest price for each one.

Is Google Ad Manager a DSP or an SSP?

Google Ad Manager is on the sell side. It's an ad server with Google's ad exchange (AdX) built in, so it works for publishers. Google's buying tool, the DSP, is Display & Video 360, which bids into AdX and other exchanges.

Can a publisher use a DSP?

A publisher can, but only as a buyer, for example to advertise its own site. To sell ad space, you work with SSPs, exchanges and an ad server. DSPs reach your inventory through those, so there's no DSP account to open.

Who pays the DSP fee, the advertiser or the publisher?

The advertiser pays the DSP, usually as a share of spend. The publisher pays the SSP, usually as a share of revenue. Both fees come out of the same advertiser dollar, which is why the bid you see is lower than what the brand paid.

Is a DSP the same as an ad network?

No. An ad network buys or bundles ad space and resells it, often with its own fixed rules. A DSP is software that bids on single impressions in real time for many advertisers. Some ad networks now buy through DSPs or run their own.

Do I need both a DSP and an SSP?

Not as a publisher. You need the sell side: an ad server plus SSPs or exchanges. Advertisers bring the DSPs. If you want help working out which sell-side partners fit your traffic, talk to MH AdX.

Next step

Pick the first step on that list you haven't done and do it this week. For most sites it's step 4, moving from one network to an ad server. Our header bidding service sets up the SSPs that bring more DSPs to your inventory.