Popunder ads remain one of the highest-paying ad formats available for website publishers. Unlike traditional display banners, popunder campaigns often deliver significantly higher CPM rates because advertisers are willing to pay more for direct user exposure.

However, there is one problem that almost every publisher encounters: very few popunder advertising networks are able to maintain a 100% fill rate. Even the best companies occasionally run out of campaigns for certain countries, devices, or traffic sources. As a result, visitors may arrive at your website without seeing any advertisement at all, reducing your overall earnings.

Fortunately, there is a simple trick that allows you to maximize your revenue while keeping your fill rate as close as possible to 100%.

The solution is to use a fallback code.

Instead of relying on a single advertising network, you can configure your primary popunder provider to automatically load another company's popunder code whenever it cannot serve an advertisement. This ensures that unsold impressions are immediately monetized by a secondary network rather than being wasted.

(Popunder Ad Networks with High CPMs)

Even better, some platforms allow you to define a minimum CPM threshold. If the available advertisement pays less than your desired CPM, the system automatically skips it and displays the fallback network instead, helping you maximize the value of every impression.

Why PopAds is the Best Platform for this Strategy

Among all popunder advertising networks, PopAds is arguably the best choice for implementing this strategy.

Founded in 2010, PopAds has built an excellent reputation among publishers thanks to its high CPM rates, worldwide advertiser base, fast payments, and extensive optimization options. It supports virtually every type of website and offers detailed controls that allow publishers to maximize revenue without sacrificing flexibility.

Link: Sign up in PopAds as a Publisher

One of its most valuable features is the ability to configure an external fallback code when creating a popunder campaign.

This means you simply paste the JavaScript code from another popunder advertising network into the fallback field. Whenever PopAds cannot deliver an advertisement, the secondary network is automatically loaded instead, helping you recover impressions that would otherwise generate no revenue.

The platform also offers an even more powerful option: minimum CPM bidding.

For example, suppose you configure a minimum CPM of $0.50. If PopAds only has an advertisement available that pays $0.30 CPM, it will automatically reject that campaign and load your fallback network instead. This allows you to maintain higher average CPM rates while still monetizing almost every visit.

The result is a much better balance between high CPM and maximum fill rate, something that is difficult to achieve using only one advertising network.

Review of this platform: PopAds, the best PopUnder Ad Network

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The Best Fallback Networks

Although almost any popunder network can be used as a backup, these three platforms stand out as the best alternatives.

PopCash (Review)

PopCash is one of the oldest and most respected companies specializing exclusively in popunder advertising.

It has worked with publishers for many years and consistently offers competitive CPM rates across a wide range of countries. Thanks to its large advertiser base, it frequently serves ads in regions where other networks may have limited inventory.

One interesting advantage is that PopCash generally allows only one popunder every 24 hours for each visitor. While this restriction may reduce the total number of impressions served, it can also improve user experience and make it an excellent secondary network when used as a fallback.

Although PopCash may not always achieve a perfect fill rate by itself, it is an outstanding choice for increasing overall revenue thanks to its strong CPM performance.

Link: Sign up in PopCash as a Publisher

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Adsterra (Review)

Adsterra is one of the world's largest advertising networks and supports multiple ad formats, including high-performing popunder campaigns.

Its biggest advantage is the enormous number of advertisers using the platform. Because of this extensive inventory, Adsterra is usually able to serve ads for virtually every country and traffic source, making it one of the most reliable options when your primary network has no available campaigns.

Although CPM rates vary depending on the visitor's location, its consistently high fill rate makes it an excellent fallback provider. In many cases, the platform can monetize impressions that smaller popunder networks simply cannot.

For publishers whose priority is avoiding unsold traffic, Adsterra is one of the safest choices available.

Link: Sign up in Adsterra as a Publisher

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Adcash (Review)

Adcash is another well-established advertising network with a global presence and millions of daily impressions across desktop and mobile devices.

Its popunder format benefits from a large pool of advertisers and sophisticated optimization technology, allowing the platform to deliver campaigns across a broad range of geographies. As a result, it is uncommon for Adcash to have no ads available, making it a dependable backup network.

While CPM rates naturally fluctuate depending on traffic quality and country, Adcash's strength lies in its ability to maintain a steady supply of campaigns. This makes it particularly effective as a fallback code behind PopAds, ensuring that valuable impressions are not lost.

Link: Sign up in Adcash as a Publisher

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Many publishers focus exclusively on finding the advertising network with the highest CPM, but fill rate is equally important. A network paying exceptionally high CPMs loses much of its advantage if it leaves a significant percentage of impressions unsold.

By using PopAds as your primary popunder network and configuring a fallback code from PopCash, Adsterra, or Adcash, you can dramatically increase your overall fill rate while maintaining excellent CPM levels.

An even better approach is to combine PopAds' minimum CPM feature with a fallback network. This ensures that low-paying campaigns are automatically replaced by an alternative provider, helping you maximize both your average CPM and your total advertising revenue.

For most publishers, this simple configuration is one of the easiest and most effective ways to increase long-term earnings from popunder advertising.