Ad Tech 101: The Full Stack Behind Every Ad You've Ever Seen

This overview is brought to you by Epom — a major ad tech provider used by 50,000+ publishers in 40 countries. Contact us today to see how we can help multiply your revenues.

You run ads, and then ads run the world. All the kudos go to brands, but an invisible force, unheard by the majority, keeps the lights on. Luckily, you know about it, but that's just the start. Today, we'll fully explore the godlike powers of ad tech. And we shall start with the basics: meet ad tech 101.

Ad tech tools are the miraculous advent for online entrepreneurs of all kinds. Outside the ad tech industry, Google and Facebook would never reach 10-figure revenue levels, millions of brands would sink into oblivion, and we'd have to pay for every app on our iPhones. There'd be no way to monetize them all.

Yet, numbers don't lie:

1. Online advertising crossed $1.08T globally in 2025. And virtually every dollar of it touched some form of ad tech on its way to a screen.
2. The global programmatic advertising market is projected to grow at a CAGR of 35.8% through 2031.
3. According to Grand View Research, the global ad tech industry market is expected to reach $1.58 trillion by 2030, growing at a CAGR of 14.4%.

How did all this become possible?

To figure this out, let's take a closer look at what the ad tech industry and ad tech trends are, and define the preferred ad tech stack for your business.

Want to understand where the ad tech growth is going? Our 2026 ad tech trends guide breaks down what's reshaping programmatic buying, identity, and measurement right now.

Ad Tech Explained

So, what is adtech, really?

The adtech meaning shifts depending on who you ask:

• publishers think of it as monetization infrastructure;
• advertisers think of it as targeting machinery;

But for everyone, it comes down to the same thing: automation that makes scale possible without hiring an army.

Think of ad tech as mission control for advertisers, a centralized system for purchasing inventory across thousands of websites and apps simultaneously, without losing your mind or your budget.

What makes it actually work? Why target audiences should care?

Data and specialized algorithms that match the right inventory type to the right end user at the right moment, all without a human having to approve each placement manually.

The underrated superpower here is visibility. Ad tech gives advertisers, publishers, and agencies a 360-degree view of campaign performance, making it dramatically easier to plan, measure, and course-correct on the fly.

Brief History and Role of Advertising Technology

Twenty years ago, advertising technology became a revolutionary breakthrough in improving the effectiveness of advertising. The rapid development of e-commerce led ad agencies to help their clients place ads on websites that would bring them maximum return on investment (ROI).

The first harbinger of the digital revolution in the ad tech landscape was the invention of the first ad server in 1995 by FocaLink Media Services. It was followed by the success of Doubleclick, an ad network and ad server rolled into one which would later become the Google Ad Manager. Ad serving technology meant the end of manual ad placement — and the beginning of the era of automated advertising and ad tech industry growth.

From the launch of Google AdWords and first ad exchanges to the rise of real-time bidding — it's been a long haul. An adtech landscape ecosystem was enriched by DSPs, DMPs, SSPs, etc. It will add up a number of other ad tech tools like CDPs and 1st-party tracking platforms after the future shutdown of 3rd-party cookies that was completed in 2025. Ad buying used to mean phone calls, spreadsheets, and handshake deals — programmatic flipped that into a millisecond auction happening 10 billion times a day. Digital advertising campaigns...

"The consumer behavior shift the industry underestimates is this: identity no longer flows through browsers — it flows through relationships. And relationships don't scale the same way cookies did."

Anton Ruin

CEO of Epom

As for the major role of ad tech in today's advertising industry, here are three highlights:

Programmatic Advertising in Ad Tech Landscape

Programmatic advertising allows publishers and advertisers to buy and sell traffic automatically, rather than negotiating prices directly. Publishers sell digital ad space; advertisers buy it; and ad tech industry is the system that makes sure neither side has to pick up the phone.

Keep reading or watch: Lina Lugova, Head of Marketing at Epom, giving an extensive overview of the programmatic advertising ecosystem.

The automated programmatic approach is based on a real-time bidding (RTB) protocol. Publishers use a supply-side platform (SSP) to list their digital ad inventory. When someone visits a publisher's website, the SSP forwards the ad request to a demand-side platform (DSP), which manages the advertiser's campaigns. The DSP initiates an RTB auction — the highest bidder wins, their ad is served, all in milliseconds.

💡 Not sure how DSPs, SSPs, and ad servers compare? We broke it down: Top 10 DSP Platforms Compared · Ad Server vs DSP: What's the Difference

AdTech vs. MarTech: The Difference

Ad tech is often confused with marketing technology, as the two industries intersect. Some people see advertising as part of an overall marketing strategy, and in a broad sense, it is. In a narrower sense, there is a difference between marketing and advertising.

Both marketing and advertising are promotional activities. Yet advertising mostly means sponsored content, so the brand always pays to place its ads on any channel, whether another website, social media, or connected TV.

Marketing is more about the holistic approach to promotion. Marketing starts with defining your unique selling proposition, buyer personas, and right channels where you'll promote your product/services. The major goal here is to learn your audience, deliver the right message, and bring more leads to your sales team. The marketing strategy includes a mix of activities, one of which is advertising.

Speaking of martech vs adtech, the relations between them are mostly the same. Advertising tools and software is a part of the marketing tech stack usually used by large brands.

Still, going deeper into the ad tech industry overview, you should draw a line of distinction from martech in the narrow sense. Ad tech is used to set up, launch, and manage advertising campaigns as well as sell and handle ad inventory management on apps or websites.

Besides ad tech, marketing technology includes a wide range of tools for marketing analytics and automation, A/B testing, message personalization, data analysis, SEO, social media management, etc. Here is a handy table illustrating the difference on adtech vs martech:

The further away, the blurrier the distinctions in the case of martech vs adtech. For example, a customer data platform has great potential to be used in advertising, although traditionally it's a tool for sales and marketing. That's why I included it in my list of ad tech software types.

Ad Tech Ecosystem: Types of Ad Tech Software

An ad tech ecosystem (sometimes called an ad tech landscape) is a collective name of all tools and software, industry players, and connections between them.

Just like veins and arteries carry blood to and from the heart, streams of supply and demand embody the intentions of advertisers and publishers. To achieve their goals, both of them use different tools. Publishers use a 1st-party ad server or a supply-side platform (SSP) to handle their inventory, while advertisers are for campaign management.

Ad networks and ad agencies can be ad tech software providers and customers of existing ad tech vendors at the same time. For example, an ad network can use a white-label ad server with its full functionality and create restricted accounts for their clients within the platform. Ad agencies can buy traffic with a demand-side platform and provide media buying services to the advertiser, etc.

Ad Server

Ad servers host, store, and serve ads on a publisher's website. Today they've evolved into full platforms for launching campaigns, managing placements, and matching publishers and advertisers in a single interface. Without ad servers, media buying would require manual HTML changes on every page.

Learn more → Download Complete Ad Server Guide · Compare Ad Server Options

Demand-Side Platform (DSP)

A Demand-side platform (DSP) is a platform that allows users to purchase inventory from various ad exchanges and supply-side platforms (SSPs) in a specially designed interface. A DSP is a crucial element in real-time bidding (RTB), where it serves as the recipient of a browser's ad-serving request. Running digital ad campaigns across dozens of publishers simultaneously used to require a small army; a DSP makes it a one-person job.

The cool thing about a DSP is that it offers even more automation than an ad server — here, you don't have to negotiate prices with publishers directly. Instead, you set your targeting preferences and CPM, then launch the campaign. And the best part: bidding rules, multipliers, and other optimization tools that spare you from babysitting your media buying.

There are two options for advertisers: use a self-serve DSP from the ad tech provider, or buy a white-label advertising platform to gain full control over their advertising. A white-label DSP is a SaaS solution that can be customized and branded as your own. Unlike a self-service DSP, a white label solution can also be integrated with custom SSPs. That means that you'll be in charge of where your traffic comes from, and get all the data transmitted from publishers.

"The biggest mistake we see with DSP setups is treating bidding rules as a one-time config. They need to be tuned continuously as traffic patterns shift"

Andriy Liulko

CSO at Epom

Learn more → Complete DSP Guide · Top 10 DSP Platforms Compared · White-Label DSP vs Self-Serve: What's the Difference

Supply-Side Platform (SSP)

A supply-side platform (SSP) is the reverse side of a DSP. It's a piece of ad tech tool designed for publishers. By using this instrument, publishers can manage, sell, and optimize inventory on their websites and mobile apps.

Just like a DSP, an SSP is based on an RTB protocol, which means that the publisher embeds an ad tag or a header to their web pages, so the user's browser could request the ad each time someone visits the website. Then, the tag will be sent forward to the SSP, which will process the publisher's data and request a suitable ad from the DSP to show it on the website.

A DSP will match the publisher's audience with the advertiser's targeting, choosing the highest bidder in the process. The highest bidder brings the publisher max possible revenue with minimal effort from the supply side.

Agency Trading Desk (ATD)

An agency trading desk is a set of tools provided by media agencies for planning, buying, and managing the advertising on various channels. We can say that this is a simplified version of the demand-side platform for those who are not ready to invest in a DSP or an in-house team at the moment. The ATD employs staff that substitutes in-house media buying teams. The drawback of this software: advertisers who use ATD services do not have direct access to the inventory.

Ad Exchange

Ad exchanges serve as middle links in real-time bidding. They are mostly used by large ad tech providers to connect DSPs to suitable SSPs and vice versa. Even though publishers and advertisers rarely have direct access to the ad exchange, their traffic and inventory usually passes through the platform before getting to its final destination.

On the way from the advertiser and publisher, both traffic and inventory can be acquired by ad networks, which will further use them for their own purposes. Summing up, an ad exchange is an open marketplace of impressions, where all existing RTB players match with each other.

Data Management Platform (DMP)

The data management platform allows advertisers to gain in-depth knowledge about their customers' behavior. Advertisers use DMP to collect data from various sources — tags on websites and mobile apps, cookies, APIs, and S2S integrations. DMPs utilize 3rd-party cookies to create temporary user profiles and segments to make behavioral targeting in a DSP or ad server possible.

Customer Data Platform (CDP)

Customer data platform collects not only 3rd-party data, but also user info provided by consent (i.e. 1st-party data). This data is also called PII (personally identifiable information), which means that a CDP creates a unified customer profile with a known name, company, email, etc. CDP collects these attributes from web and mobile analytics tools, CRM, transactional systems, subscriptions and newsletter signups.

In the past decade, CDPs were mostly used by marketers to consolidate data about their leads and customers. Yet, in 2025, when 3rd-party cookies were completely phased out by Google, ad tech apparatus will also adopt this approach to data collection. With no access to 3rd-party data, ad tech vendors and networks will have to find a way to retrieve 1st-party data from users, and a CDP might be a pretty good shot in this battle.

Inventory and Ad Quality Scanning Tools

Ad fraud affects ads globally, with malicious bots now accounting for 37% of all internet traffic. Based on Epom observations, the problem is most acute for smaller networks running open exchange traffic without quality controls. Inventory and ad quality scanning tools verify creatives before they serve and flag suspicious supply. Epom DSP uses GeoEdge to protect partners on the supply side.

Inventory and ad quality scanning tools are ad tech means which help to avoid both threats. Before being served on the website, the ad should be verified with an ad quality scanning tool, and vice versa. For example, Epom DSP uses the GeoEdge solution to weed out dubious creatives and protect our partners from the supply side.

AdTech Trends: Revealing the Future of AdTech

The ad tech industry layout in 2026 looks meaningfully different from even two years ago. Three ad tech industry trends are reshaping how programmatic works:

AI and ML Impact on Programmatic Advertising

AI and automation are handling bid optimization, creative rotation, and audience modeling tasks that used to require dedicated analysts. Based on Epom observations, the teams getting the most from AI aren't automating everything — they're using it to eliminate busywork while keeping human judgment on strategy and creative.

Cookie Deprecation and Rise of the Third-Party Cookie Alternatives

Identity without cookies is no longer a future problem. With 3rd-party cookies gone, the industry has largely moved to first-party data, CDPs, contextual targeting, and universal ID solutions like UID2. Publishers and advertisers who started building first-party data pipelines early are pulling ahead.

Growth of Programmatic TV and Retail Media Networks

Retail media and CTV have become primary channels, not experiments. Retail media networks offer purchase-intent data that behavioral cookies never could. CTV is growing faster than any other programmatic channel.

Learn more → Ad Tech Trends 2026 · Download the 2026 Ad Tech Industry Report

How to Choose the Right Ad Tech Tools for Your Business

Choosing the right ad tech solutions is all about having the right ones for your specific role in the ecosystem. A publisher's stack looks nothing like an advertiser's, and confusing the two is how budgets disappear.

Ad Tech Stack for Networks

The major goal of ad networks is to match publishers and advertisers and help them make the most of their ad serving. Let's see which ad tech tools are a must-have for networks.

• Ad server. An Alpha and Omega of an ad network. As most ad networks have direct connections to their clients, an ad serving platform is exactly what they need to streamline the process of client management.
• A white-label ad server is one of the most sophisticated ad tech tools with customizable targeting, rules and permissions, powerful API, and 800+ other features.
• DSP & SSP. Even though ad servers usually have RTB integration, some networks rely heavily on programmatic media buying. If you're one of them, consider setting up a white-label DSP, SSP, or both, if you deal with both supply and demand partners directly. A white-label programmatic platform allows you to unite all SSPs and DSPs in one place and saves up to 30% of your ad spend, while skipping middle links in ad tech vendors.
• DMP (Data management platform.) Ad networks can enrich their campaign targeting with additional data by connecting their DSPs and ad servers to the data management platform. DMPs can combine both 3rd-party data that you can collect using cookies and 1st-party data derived directly from companies you're working with.
• Ad exchange. There is no need to build your own ad exchange, but ad networks may directly buy traffic and inventory from ad exchanges that belong to prominent ad tech brands.
• Ad quality scanning tools. Those software which help ad networks maintain a good reputation and minimize fraudulent traffic and inventory coming through their platform.

Ad Tech Stack for Agencies

• Ad server. Small ad agencies usually don't need it, but if you run a large ad agency that not only creates advertising strategies, but also runs ad campaigns on behalf of your clients, you can try a basic or standard plan of an ad server. Little chance that you'll regret it!
• DSP. Ad agencies might not need a white-label solution and can go for a self-serve DSP if the number of impressions of their ad spend doesn't exceed tens of thousands of dollars. Learn more about the difference between a white-label and a self-serve DSP.
• ATD. This platform streamlines the agency's communication with clients. Agencies can offer their advertising services with an agency trading desk. It makes sense to build your own ATD or utilize a white-label solution from an ad tech company.
• Inventory scanning tools. Similar to ad networks, ad agencies have to maintain the high quality of inventory they offer to their clients.

Ad Tech Stack for Advertisers/Brands

• Ad server. This ad tech instrument helps your brand take advertising in-house. Especially beneficial if you have direct publisher connections and already know which websites you'd like to serve your ads.
• DSP. You can use a white-label DSP, if you want to implement a hardcore programmatic in-house strategy. This way, you'll take over all media buying activities and will be able to make the most of your ad campaigns with the least money spent.
• DMP. Is there any brand that wouldn't like to learn more about their audience? A DMP can handle it, while significantly increasing the effectiveness of your ad campaign.
• CDP. In the post-cookie era, a CDP may substitute a DMP.
• Ad quality scanning tools. To make sure your ads don't violate any policies and are malware-free, you can verify them with these ad tech instruments.

Ad Tech Stack for Publishers/App Developers

• Ad server. If you have several websites and/or apps under one umbrella, you may benefit from having an ad server under that same umbrella. With this tool, publishers can connect multiple demand partners and manage all monetization campaigns in one interface.
• SSP. This platform is similar, with the exception of selling your inventory programmatically. This means less hassle for you, as you don't have to look for direct partners and negotiate placement conditions with them. All you need to do is specify your requirements, desired price floor, and list your inventory in an SSP.
• Inventory scanning tools. Prove yourself as a reputable partner for your demand counterparts: scan each placement and make sure that you don't have any technical issues on your website.

Ad Tech Tools Comparisons

• Ad servers comparison.
• Self-serve DSPs comparison.
• DSP comparison.

Ad Tech: Summary

Ad tech toolset takes your advertising to a new level. A range of software that the ad tech ecosystem includes — ad server, ad exchange, agency trading desk, demand-side and supply-side platforms, ad networks — allow their users reach their goals by making digital advertising more accurate and cost-effective.

FAQs

• What is an ad impression discrepancy?

  An ad impression discrepancy is the difference in impression count reported by two or more advertising platforms (for example, a DSP, SSP, or ad server). It happens because partners use different counting rules, tags, devices, and measurement methodologies.

• How do you calculate discrepancy correctly?

  To calculate discrepancy, subtract one partner’s count from the other, then divide the difference by the reference count and multiply by 100. This formula helps confirm whether the discrepancy is within an acceptable range.

• What is an acceptable average discrepancy rate?

  In digital advertising, an average discrepancy of up to ~10% is considered normal. Anything higher is a signal to review tags, platforms, vendors, devices, and how impressions are counted across partners.

• Why do publishers and advertisers see different numbers?

  Discrepancies occur because impressions are counted at different points (request vs render), across different devices, or filtered differently for invalid traffic. Ad blockers, missing macros, and unmatched tags also prevent platforms from matching impressions correctly.

• How can an ad discrepancy be minimized in practice?

  To save time and budget, partners should align measurement models upfront, confirm tags and macros, use the same reporting windows, and audit vendors regularly. Clear methodology and transparent communication matter more than chasing “perfect” numbers.