Advert technology, tool by tool, for the people selling ads

Advert technology is the software that buys, sells, places and measures online adverts. Ad tech covers the tools advertisers use to bid for ad space, the tools publishers use to sell it, and the systems in between that run the auction, serve the ad and check it was real. Every display ad you see passed through several of these tools first.

Here's the problem. If you run ads on your site, you get emails full of ad tech words: SSP, wrapper, CMP, DSP, sellers.json. Most explainers are written for advertisers, so they never say which of these tools you, the seller, actually need. That's how publishers end up paying for tools they don't use and missing the two or three that would earn them more. If you're newer to how ads get sold, our guide to programmatic advertising for publishers is the gentle start.

This guide maps advert technology from the seller's side: every tool in one table, the path one advert takes, and what to add at each stage of your site's growth.

What is ad tech, in plain English?

Ad tech is short for advertising technology, and it means the same thing as advert technology. "Advert" is just the UK word. Buyers use it to choose who sees an ad and what to pay. Sellers use it to decide which ad fills each space and at what price.

The simplest way to picture it is a market with two sides and a trading floor.

• The buy side is advertisers and their agencies. Their main tool is the demand-side platform (DSP), which bids on ad space for them.
• The sell side is publishers: websites, apps and streaming channels. Their main tools are the ad server and the supply-side platform (SSP).
• The middle is the ad exchange, where bids meet ad space in an auction that takes a fraction of a second.
• Around all of it sit the helpers: consent tools, data platforms, identity providers and verification vendors.

Most of this trade is programmatic, which means software makes the deal instead of people sending insertion orders. IAB Tech Lab calls its OpenRTB standard the foundation of that ecosystem. OpenRTB is the shared language that lets an SSP put a single ad impression up for bids in real time.

The advert technology stack, tool by tool

An ad tech stack is the set of tools one company uses to buy or sell ads. Here's every common tool, who runs it, and what it does. The last column is the part most guides skip: whether a publisher ever logs in to it.

Two standards hold the sell side together, and they're files, not tools. ads.txt lists who may sell your ad space, and sellers.json lists who an SSP pays. IAB Tech Lab explains that ads.txt stands for Authorized Digital Sellers: it lets you publicly declare the companies you allow to sell your inventory. Our ads.txt guide for publishers covers the file line by line.

The ad server

The ad server is the referee. Your direct deals, your programmatic demand and your house ads all compete inside it, and it picks the winner for each slot. Google Ad Manager is the ad server most publishers run, and it also has deal tools built in. Google's own help page says Programmatic Direct automates the negotiation and sales of your direct-sold inventory.

SSPs and ad exchanges

An SSP is your shop window to thousands of buyers. In practice the SSP and the exchange are often the same company and the same login. We cover the difference in what a supply side platform does, and the buyer's mirror image in DSP vs SSP.

Header bidding

Header bidding lets several SSPs bid before your ad server makes its choice, so they compete on price instead of waiting in line. Prebid, the open-source project behind most setups, describes it this way: Prebid collects bids before the ad server is called, and the ad server makes the final decision. Prebid.js runs in the browser, and Prebid Server does the same job on a server.

How one advert travels through ad tech

A single display ad passes through the stack in a set order, and the whole trip takes about as long as the page takes to load. Here's the path for a typical site running Google Ad Manager with header bidding.

1. The page loads and the CMP runs. The consent tool reads or asks for the visitor's choice and stores it as a consent string every vendor can read.
2. The header bidding wrapper calls the SSPs. Prebid sends each SSP the ad slot, the display sizes that slot accepts, the page and the consent string.
3. Each SSP sends a bid request to its buyers. The request travels in OpenRTB format through the exchange to many DSPs at once.
4. DSPs decide and bid. Each DSP checks the user, the page and its advertisers' rules, then returns a price or passes.
5. The best header bids go to the ad server. The wrapper passes the top prices to Ad Manager as key-values.
6. The ad server picks the winner. Ad Manager compares those bids with your direct deals, its own exchange and your price floors.
7. The creative loads and gets counted. The winning ad renders, the impression is counted, and verification tags check viewability and fraud.

Every hop in that list is a place where money leaks or a bid gets lost. Slow SSPs time out. A broken consent string makes buyers in the UK and EU pass. A missing ads.txt line means a DSP skips you without telling you. The detail of steps 3 and 4 lives in our explainer on real time bidding.

Which ad tech a publisher actually needs

Good ad tech for publishers is a short list: you need far fewer tools than the stack diagram suggests. Add them in this order, and only when the one before stops being enough.

Our honest advice: don't jump to stage 4 tools before stage 3 is clean. When we review a publisher's setup, the money is usually lost in the boring layers. Think missing ads.txt lines, consent strings that don't reach bidders, or a wrapper with ten SSPs where four would bid higher. The steps for stage 3 are in our Prebid.js setup guide.

Ad tech vs martech

Ad tech pays to reach people you don't know yet; martech talks to people who already know you. The two overlap in the data layer, which is why the terms get mixed up.

For a publisher, the overlap is your first-party data. Newsletter sign-ups and logins live in martech tools, but they become ad tech the moment you use them to build audiences buyers will pay for.

Who pays for adtech advertising tools?

Mostly, the money for adtech advertising tools comes out of the ad spend itself. Each layer between the advertiser and you keeps a share, so the price a brand pays is higher than the price you receive.

• DSPs usually charge advertisers a share of spend or a platform fee.
• SSPs and exchanges usually keep a share of each winning bid before paying you.
• Ad networks pay you a revenue share. AdSense, for example, publishes its share on its own help pages.
• Ad servers, CMPs and analytics tools are often free at small scale, then charged per impression or by subscription.

Exact fees vary by partner and are rarely public, so we won't quote a single figure. Regulators have looked hard at this gap.

The UK's Competition and Markets Authority studied the ad tech chain in its online platforms and digital advertising market study, published on 1 July 2020. It found that competition "is not working well in these markets".

So here's the practical takeaway. Ask every partner what share it keeps, and check its sellers.json entry matches what it told you.

What changed in advert technology in 2025 and 2026

The biggest ad tech news of the last two years was legal, not technical. Here's what happened, with the primary source for each, and what it means for a publisher's stack.

None of this means you should rip out your ad server. It means two things. First, keep more than one demand source so no single company's rule change hits all your revenue. Second, read Ad Manager's release notes for the next year, because auction changes ordered by the court will show up there first. Our post on ad networks vs ad exchanges explains why mixing demand sources matters.

Frequently asked questions

Is advert technology the same as programmatic advertising?

Not quite. Advert technology is all the software involved, including ad servers and consent tools. Programmatic advertising is the automated way of buying and selling ads that much of that software makes possible.

Is Google AdSense ad tech?

Yes. AdSense is an ad network with its own ad serving built in. It's the simplest piece of ad tech a publisher can run: one code snippet, and Google handles the buyers, the auction and the payment.

What is an ad tech stack?

An ad tech stack is the set of tools one business uses to buy or sell ads. A typical publisher stack is a CMP, an ad server, a header bidding wrapper and a handful of SSPs, plus ads.txt.

Do small websites need an ad server?

Not at first. AdSense alone is fine while you're small. Move to Google Ad Manager once you want direct deals, price floors or a second demand source, because those need an ad server to compete fairly.

What does an ad tech company do?

An ad tech company builds or runs one of the tools in the stack: a DSP, an SSP, an exchange, an ad server, a CMP or a verification service. Some run several. Most earn a share of the ad spend that passes through their tool.

Is ads.txt part of ad tech?

Yes. ads.txt is an IAB Tech Lab standard, a public text file on your domain that lists the companies allowed to sell your ad space. DSPs check it before they bid, so it's one of the cheapest pieces of ad tech to get right.

Next step

Advert technology looks huge from the outside, but a publisher only needs a handful of tools, added in the right order. If you're at stage 2 or 3 and want more buyers competing for every slot, see how our header bidding setup works, or ask for a free review of your current ad stack.