What is Ad Stacking & 3 ways to prevent it?

Last updated: January 18, 2023 | by Kean Graham

This post was most recently updated on January 18th, 2023

What is ad stacking?

Ad stacking is literally the placing of ads on a page in such a way that they overlap, or stack, one another or other content. For a less reputable publisher, this has the advantage of getting payments for multiple ads within the same area of screen real estate, as all will get counted as an impression. For an advertiser, it means less value as some or all of their ad is not viewable by a user, and if anything is still viewable it has less visual impact. Not surprisingly, ad stacking is a Google violation, and can in severe cases lead to account suspensions or bans.

A form of Invalid traffic

We refer to ad stacking as what we call vague invalid traffic. Rather than obvious invalid traffic, such as bot activity – think multiple clicks or views on a site in a regular pattern, or too many in a short duration that couldn’t possibly be human activity – invalid traffic is more difficult to identify.

What are the consequences of ad stacking and invalid traffic?

The most obvious is a drop in revenue, from advertiser and ad network clawbacks. If impressions are identified as invalid, the money you earn from that impression will be returned to the advertiser and shown as a negative amount on your payout invoice. It’s painful to see impressions and revenue rise during the month and then have that revenue taken away at the end of the month – even several months after the impression was initially delivered.

The second and potentially more serious consequence is that repeated and consistent invalid traffic can lead to reduced bids from advertisers or ad networks or even a complete ban; a loss of an AdSense account, or an advertiser’s refusal to bid on your impressions entirely.

Finally, consistent invalid traffic, even at a low level, leads to a loss of your reputation amongst advertisers and networks, and this is impossible to quantify; imagine you were a shopkeeper in a small town and your produce was occasionally bad. You might not notice, and it might not be enough for anyone to complain, but trade might drift away.

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Unintentional ad stacking

It’s important to note that a lot of the time, ad stacking is unintentional. Most publishers that stack ads don’t realize they’ve done it. It can happen if the website code doesn’t render correctly on a certain viewport size, or if a different ad size serves that conflicts with content. And it’s hard to spot with the naked eye.

So how do we prevent it?

The first way is manually. It is possible to use browser tools to check different viewport sizes – Mozilla and Chrome have developer tools that allow you to see how the site appears across different mobile, tablet, and desktop sizes. Schedule a time each month to check a selection of pages across all available sizes; look carefully at ad borders and make sure nothing looks out of place.

You can also monitor campaign stats. Ad stacking could exist if impressions are solid, or higher than normal while at the same time clicks are low or falling.

The second way is automatically via your own coding and tools. It requires advanced coding and a huge amount of work – we know, we’ve already done it!

A better third way?



The third way is automatically using Traffic Cop, the tool Monetize More built that impressed Google so much they gave us an innovation award.

We noticed there wasn’t anything commercially available that detected not only ad stacking but other policy violations as well such as overly aggressive refreshes and ads serving while unviewable. Traffic Cop detects these violations and tells you where it is and how to fix it. Once it’s fixed, you can mark it as solved and Traffic Cop will recheck.

Traffic Cop also blocks bot traffic, even sophisticated bots that mimic human behavior, slashing your revenue clawbacks and helping to increase your site’s reputation amongst advertisers. The standard of impressions you can provide will unlock higher RPMs from the most premium of sources.


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