What Is an Ad Network? How Ad Networks Work

What is an ad network?

An ad network is a company that collects ad space from many publishers, such as websites, apps and games, and sells it to advertisers in one place. The advertiser gets reach across thousands of sites without signing a deal with each one, and the publisher gets paid for ad space it could not sell on its own. The network handles the sales, ad serving, tracking and payments, and keeps a share of what advertisers pay.

The US Federal Trade Commission put it plainly in its 2007 statement on Google and DoubleClick: ad networks are intermediaries that “aggregate or purchase advertising inventory from a group of websites and sell this inventory to advertisers or ad agencies, taking a share of the revenue from each sale.” That definition still holds, even though most networks now also sell app inventory and buy through automated auctions.

How ad networks work, step by step

Advertisers bring budgets and ads. Publishers bring ad space and an audience. The network matches the two, and a single ad goes through five stages:

1. The advertiser buys. It sets up a campaign: budget, price, countries, devices, audience and the ads themselves.
2. The publisher joins and places a tag or SDK. The network reviews the site or app, then gives the publisher a code snippet for websites or an SDK for apps, tied to ad units such as a banner, a video slot or a rewarded placement.
3. The ad request. When a user opens the page or reaches the placement, the tag or SDK asks the network for an ad. The request carries context: the ad size, the app or page, the country, the device and, where the user allows it, an advertising ID.
4. The ad serve. The network picks the campaign that fits the request and is worth the most to it, then returns the ad. If nothing fits, the request goes unfilled, and that is what your fill rate measures.
5. Measure and pay. The network counts impressions, clicks and conversions, filters out invalid activity, bills the advertiser, and pays the publisher its share on a set schedule.

Steps 3 and 4 take a fraction of a second. Step 5 takes weeks, because networks finalize numbers after filtering invalid traffic, which is why “estimated” earnings can change later.

How ad networks charge advertisers and pay publishers

The pricing model decides what the advertiser pays for, and so who carries the risk that the ad does nothing.

Publishers rarely see these prices directly. Most networks pay a share of what advertisers spend and report it as eCPM: your earnings per 1,000 impressions, whatever model the advertiser bought on. That makes CPM, CPC and CPA campaigns comparable in one number. eCPM vs RPM explains the publisher metrics, and CPM vs CPC vs CPA covers the choice from the advertiser’s side.

Types of ad networks, with examples

Ad networks are usually grouped by what they sell and how they charge. Many networks fit more than one group.

Vertical networks

A vertical network focuses on one topic or audience, such as gaming, finance, health or technology. Advertisers pay more for that focus.

Premium networks

A premium network accepts only well-known publishers with large, brand-safe audiences and sells their inventory at higher prices, often to big brands. New sites rarely qualify.

Performance and CPA networks

A performance network sells on results: clicks, installs, leads or sales. The FTC’s 2010 statement on Google and AdMob described performance mobile ad networks as ones where advertisers “often buy ad space through auction rather than through sales relationships, and pay for the advertising on a ‘per click’ or other direct response basis.” At the far end are CPA networks, which pay only when an action is confirmed. What is a CPA network? covers that model in depth.

Mobile in-app networks

Mobile networks sell ad space inside apps and games: banners, interstitials, native ads and rewarded video, delivered through an SDK. Google describes AdMob as “a mobile ad network and monetization platform for mobile developers”. Most apps run several mobile networks at once through ad mediation, so they compete for each request.

Offerwall networks

An offerwall network lists offers from many advertisers, such as installing a game and reaching a level or completing a survey, inside a wall in the publisher’s site or app. Users complete offers for the publisher’s own currency, and the publisher earns per completed offer. It only fits offers whose advertisers accept rewarded users. What is an offerwall? explains how walls work.

Affiliate networks

An affiliate network connects merchants with affiliates who promote their products, usually for a commission on each sale. It overlaps heavily with CPA networks. Offerwall vs affiliate links compares the two for publishers.

The best-known example of a general network is Google AdSense. Google’s own comparison page says “AdSense acts as an ad network, providing you access to demand from advertisers”, for web inventory, while AdMob does the same for apps (checked on October 20, 2026).

Ad network vs ad exchange vs SSP and DSP

These terms get mixed up because one company often runs several of them. The difference is in what each one does.

• Ad network: buys or collects inventory from its publishers, packages it, and resells it to its advertisers. The network sets or controls the price and decides which ad shows.
• Ad exchange: a marketplace, not a reseller. The FTC’s 2007 statement says exchanges “aggregate inventory by providing platforms for advertisers and publishers to list and bid for inventory.” Each impression is auctioned in real time, and ad networks themselves can buy and sell on exchanges.
• SSP (supply-side platform): software a publisher uses to sell its inventory to many exchanges and buyers at once, with price floors and rules.
• DSP (demand-side platform): software an advertiser or agency uses to bid on inventory across many exchanges and SSPs from one place.

The auctions behind exchanges, SSPs and DSPs mostly speak one shared language, OpenRTB. According to IAB Tech Lab’s OpenRTB page, the group that wrote it was formed by supply- and demand-side companies in November 2010, and the spec defines how a single impression is put up for bid in real time. DSP vs SSP goes deeper into the two platforms.

Here is how a classic network compares with an exchange and two pay-per-result channels:

A short history of ad networks

Ad networks grew up with web display ads, because most sites were too small to sell ads themselves. The FTC’s 2007 statement captures the market at an early turning point. It called ad networks and ad exchanges the “two types of ad intermediation products” and listed recent deals, such as Yahoo! buying the Right Media Exchange and Microsoft buying the AdECN exchange. It also noted that DoubleClick sold ad serving tools and did not buy or sell ad inventory. Google closed its purchase of DoubleClick on March 11, 2008, according to Google’s AdWords blog.

Mobile came next. In its May 2010 statement on Google’s proposed $750 million purchase of AdMob, the FTC called the two companies “the two leading mobile advertising networks” and explained that app developers “rely on mobile ad networks to sell advertising space that they cannot effectively sell on their own.” It voted 5-0 to let the deal go ahead, citing Apple’s entry into mobile ads.

Real-time bidding then moved much of the market from fixed network deals to auctions, with OpenRTB as the standard. To fight fake and resold inventory, IAB Tech Lab released ads.txt in June 2017, later extended to apps as app-ads.txt, and the OpenRTB working group finalized sellers.json on July 31, 2019. In apps, mediation and in-app bidding now let many networks compete for each request, alongside performance formats such as rewarded video and offerwalls.

How publishers choose an ad network

Judging networks by eCPM alone is the most common mistake. A high eCPM that fills half your requests can earn less than a cheaper network that fills nearly all of them. Compare these five things instead.

1. Revenue per 1,000 ad requests

Multiply eCPM by fill rate. That gives what the network actually earns you per 1,000 requests your page or app sends, including the empty ones.

2. Payment terms

Check the minimum payout, when you are paid, the methods and the fees. As one reference point, Google’s AdSense payment timeline finalizes the previous month’s earnings on the 3rd and issues payment between the 21st and the 26th, if your balance reached the payment threshold by the 20th (checked on October 20, 2026).

3. Formats and integration

The network must support the formats you need (display, native, video, rewarded or an offerwall) on your platforms, without slowing your pages or bloating your app. Check SDK size and whether it works with your mediation platform.

4. Content and traffic policies

Every network has rules about what content it will monetize and what traffic it accepts. Most ban buying cheap traffic, incentivizing clicks and placing ads where they get clicked by accident. Breaking them can get an account closed and its earnings withheld.

5. Exclusivity, support and reporting

Avoid contracts that stop you from using other networks unless the price is worth it, and look for reports you can split by country, format and placement. How much can an offerwall earn? shows how to estimate a performance format before you commit.

How ad networks fight invalid traffic

A network sells trust as much as reach. If advertisers pay for bots, they leave. Google’s AdSense help page on invalid traffic defines it as “any clicks or impressions that may artificially inflate an advertiser’s costs”, whether deliberate fraud or accidental, and lists examples such as publishers clicking their own ads, automated clicking tools and robots, and encouraging users to click.

The industry standard for measuring it comes from the Media Rating Council. Its invalid traffic standards addendum splits it into two tiers:

• General invalid traffic (GIVT): traffic caught by routine filtering with lists and standard checks, such as known invalid data center traffic, bots, spiders and crawlers, and non-browser user agents.
• Sophisticated invalid traffic (SIVT): harder cases that need advanced analytics, cross-checking or human review, such as emulators and automation tools, hijacked devices, and people paid to generate invalid activity.

Networks combine several defenses against both:

• Publisher review before approval, and ongoing checks of traffic sources after it.
• Filtering and pattern checks: known data centers and bots are removed before billing, and odd patterns, such as click rates far above normal or conversions seconds after the click, are flagged.
• Supply chain transparency through ads.txt, app-ads.txt and sellers.json, so buyers can check that the seller of an impression is authorized to sell it.
• Holding and reversing earnings tied to invalid activity, which is why estimated earnings can drop before payment.

Rewarded formats need extra care. The MRC lists “incentivized human invalid activity” among its SIVT examples. A rewarded user is valid only on an offer built for rewarded users, where the advertiser knows the user was rewarded and pays for a real action. Never reward users for clicking ordinary ads. Incentivized traffic explained covers where the line is, and Ad fraud and bot traffic lists the warning signs to watch in your own data.

Frequently asked questions