What Is Ad Stacking? The Dangers Of Hidden Ads

Sam Carr | April 8th, 2021

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Do you often see low click through rates on your display ads? Well, you could be the victim of ad stacking!

Display ads are one of the most used digtial campaigns online. With strategic planning, you can reach thousands of prospects with well-timed ads that are visually eye-catching.

But there’s a problem, and it’s in the form of ad fraud. Data from our recent study showed that display ads suffer from the most fraudulent activity, with 36% of all clicks being fraudulent.

One of the main reasons for this high figure is that webmasters have a much higher incentive to commit ad fraud when they earn money from every ad click.

How do webmasters do it? One fraudulent technique is ad stacking which they use to increase their revenue without advertisers realizing. Unfortunately for advertisers, it costs them money and skews their vital marketing data.

To find out more about ad stacking, in this guide, we explain what it is, how it works, and how you can protect your advertising campaigns.

What Is Ad Stacking?

what is ad stacking

Ad stacking is a type of ad fraud that involves layering multiple display ads on top of each other in one ad placement. To the average user, they can’t see there’s more than one ad. However, there can actually be several ads behind the first ad, but only the top ad receives real human impressions. 

It’s a very common tactic on dodgy websites that are often solely made to defraud advertisers.

And while the tactic is sometimes unintentional, in most instances, it’s done on purpose so a webmaster can make more money from their website.

For webmasters gaming the system, they can earn a substantial amount. But for advertisers, it means wasted ad budget, no real eyes on their ads, and ultimately no conversions.

How Ad Stacking Works

ad stacking example

For many webmasters, ads are an essential part of their website that they include within their content to earn ad revenue.

Unfortunately, not all webmasters are the same, and some lazy ones will always try to game the system.

Ad stacking (or ad stuffing) is a straightforward ad fraud technique that can earn a lot of money with very few users.

For many ad programs (including Google AdSense), website owners receive a CPM (cost per 1,000 impressions) which can vary from $1 to $50+ depending on different factors.

But in order to get paid, the ads need to show in a user’s viewport or screen to register as an impression.

And that’s why publishers sometimes stack ads instead of putting them all over the page. It increases the chance they’ll get money for the view.

Here’s an example of ad stacking in action.

A webmaster might stack 10 ads from Google’s Display Network across their webpage. Once the stack of ads is live, to users, it looks like there’s one advertisement like so.

google display example

For the ad on top, when a user clicks on it, the advertiser will get their money’s worth and the user will be redirected to their website. But the nine other advertisers lose out.

This is what is actually loading behind the ads on the top.

ad stacking example

No real human eyes saw their ad, and they didn’t receive any clicks. But since their ad was in the user’s viewport, they would be charged for the impression. And with 1,000 impressions costing anywhere from $1 to $50+ they’ve effectively been defrauded out of their advertising budget.

This can happen on any website, and it’s difficult for advertisers to tell when it’s happening.

From an advertiser’s perspective, it’s difficult to trace and identify ad stacking. From looking on websites, you may notice nothing at all.

But that’s unless you’re at the bottom of the stack, which means you’ll have a very low (if not zero) click through rate. That’s a classic sign of ad fraud and, more specifically, ad stacking.

Keep in mind the way the fraudulent activity affects your campaigns is more than just the loss of money. It also skews your data.

You’ll have no idea if any consumers saw your ads, which makes it difficult to understand if your campaign is effective or not.

This can prove frustrating or baffling for advertisers, as a webmaster may tell you your ad received thousands of impressions. Yet no one bought anything.

Preventing Ad Stacking

The good news is there’s a way to stop ad stacking from ruining your campaigns and wasting your budget.

Ad networks such as Google use their own tech to check for illegitimate clicks and paid search anomalies.

These are normally manual inspections. For example, Google AdSense does its checks manually (rather than with AI in real-time). And that makes avoiding ad stacking slow going.

An alternative approach is to perform your own inspections on websites that are running your ads.

This is pretty straightforward and one of the easier types of ad fraud to detect by yourself. All you need to do is check your campaign data and look for ads with really low CTRs. You then need to check what websites they were placed on and if they’re engaging in any ad stacking or other fraudulent activities.

The downside? It’s a very manual process. This makes it time-consuming on your side when you could be focusing on making your campaigns deliver conversions.

Instead, you’re left wasting time checking to see if a webmaster has stacked your ad in a group of others. But thankfully, there is a much quicker way, and we’ve got a fantastic resource that will help save you hours of time.

How Our Exclusion List Can Help

Ad stacking isn’t the most notorious form of ad fraud, yet it’s one of the most damaging to the industry.

It’s also one of the most frustrating as it ruins your hard work. All because of a webmaster trying to make a bit more cash.

Ultimately, this fraudulent activity costs you money, skews your data, and wastes your time.

You can try and prevent it by monitoring your ad accounts and checking your display placements across different websites.

But the last thing you want to be doing is running ad campaigns and then double checking if they’re even working properly.

To save you hours of your time, we’ve put together a super helpful resource that you can take advantage of today.

From working with our clients, we’ve tracked millions of websites and found over 30,000 that don’t result in conversions. And the list is free, so you can easily exclude them from your ad campaigns.

The list includes over 60,000+ apps, channels, and websites you can exclude from GDN immediately. And the list is regularly updated every month with new websites from our client’s data.

Get instant access to the free exclusions list below!

Download The Full Report

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