How do you optimize and increase your ad fill rate?

Upward graph representing an increasing ad fill rate

Most publishers require a steady and dependable stream of advertising revenue in order to fund their operations. That’s why publishers focus on monetizing every impression that they can — to maximize their advertising revenue. This is one of the reasons why ad fill rates exist and why they’re so important. Generally speaking, the higher the ad fill rate, the higher the ad revenue (within reason).

Understanding what an ad fill rate is, how it’s calculated, and how to optimize yours, will enable you to maximize your ad revenue.

What exactly is an ad fill rate?

The term “ad fill rate” is a metric that represents how many of your ad units were served out of all the ads requests sent to an ad server.

Ad fill rate is what helps you understand how your inventory is being utilized. Therefore, your ad fill rate validates the market demand for your inventory. As such, it’s an important key performance indicator (KPI) in your overall website monetization efforts.

For example, a low ad fill rate could indicate that you have too much inventory. More importantly, it indicates that you are not seeing enough demand from advertisers.

The general goal for all publishers is to monetize every last impression at the best possible bid. So, when there’s a lull in ad revenue generation, the first reasonable conclusion would be that the website in question is in need of more demand — i.e., advertisers to meet their supply (versus adding more ad units on the page).

How do you calculate it?

Since ad fill rate is a ratio, it’s expressed as a percentage. To figure out your website’s ad fill rate, you can use this simple formula:

Ad Fill Rate = (Total Ad Impressions ÷ Total Ad Requests) x 100

For example, depending on your ad layout, let’s say that your website sends out 10,000 ad requests. Realistically, however, not all of them would result in an ad being displayed. Let’s say only 7,500 of your ads were actually served from those ad requests. This results in a 75% ad fill rate.

Why isn’t my fill rate at 100%?

You want your ad fill rate and your eCPMs to be equally as high, if possible, to ensure that your content is optimized and generating revenue. Having said that, there are several factors that could be impacting an otherwise perfect ad fill rate:

1. Technical errors

The ad tech world is a complicated one, as it has a supply chain with its fair share of nooks and crannies. There are many overlapping stakeholders involved in this supply chain, like SSPs who double as ad exchanges. Everyone is working within the ad serving ecosystem to measure the effectiveness of their ad campaigns to see how they can do better.

Between a user loading your web page and viewing the rendered ads, hundreds of events have already occurred. These events happen in milliseconds, which could allow for technical errors. It takes technical expertise, like an entire Ad Ops team, to reduce the errors contributing to your low fill rate.

2. A lack of demand

As mentioned earlier, a lack of demand is often the biggest culprit of a low ad fill rate. Most new website owners have the common belief that selling ad space is as easy as breathing. However, quality matters as does quantity.

If you don’t have enough of a premium inventory to offer, advertisers are going to move on to someone who does — leaving you with a lower fill rate.

Take a closer look at your traffic analytics to get a better idea of who’s coming to your website. Understand how this information would be attractive to advertisers.

3. Compatibility

Not all ads are created equally. Some may not render on all browsers, devices, or operating systems. It could be as simple as the browser being outdated or even the operating system (OS) needing an update.

The most important thing to remember is that you want to run the correct mobile ad formats as advertisers are increasingly targeting mobile users. It’s the best way to ensure that your ads will render on different device types, so you can cross this factor off your low fill rate list.

4. Page latency

Virtually all players in the digital advertising ecosystem have to deal with page latency from time to time, which can severely impact your impressions and analytics.

Moreover, if your website encounters latency often, advertisers will jump ship to publishers with a better page load speed.

Run your website through Google’s Pagespeed Insights to see your Core Web Vitals. This free tool was built for website owners to measure their page speed, identify their bottlenecks, and learn how to optimize them.

5. A reporting discrepancy

You may have noticed that your traffic in Google Analytics may not match up with a different website tracking tool you use. The same thing happens between ad servers and demand partners. Once an ad request is sent to the demand partners, the ad servers count it as an ad impression. However, demand partners only count impressions for ads that are rendered on your web page and in the user’s view.

This often causes a discrepancy in your ad fill rates because it sends back a faulty report — which costs you revenue.

6. Adblockers

Adblocking is a tough issue to deal with because if we’re being honest, most users dislike interruptive and annoying ads. What’s worse is that some of the adblockers out there tend to block ad networks rather than ad calls, allowing the ad request to go through but never rendering on the page.

Unfortunately, adblockers trump optimization, which undoubtedly contributes to a low fill rate.

While you may not be able to control which users leverage an adblocker, you can mitigate your revenue loss and drop in fill rate with a dedicated Acceptable Ads provider like Blockthrough. You can learn more about adblockers and revenue recovery in our guide.

How can I optimize my ad fill rate?

While your fill rate won’t ever be consistently 100% — and maybe never at 100% at all — it’s still necessary to optimize your fill rate for maximum revenue. Here are a few ways to do that:

  • Perfect your ad targeting: Implement advanced targeting such as contextual and behavior targeting to ensure you’re displaying the most relevant ads possible. This will improve user experience as well as your ad revenue.
  • Subscribe to quality ad networks: The quality of your ad network and its supply will significantly contribute to increasing your fill rates. For example, if you run a larger website, selecting a small ad network won’t help you meet the necessary demand which results in low fill rates.
  • Improve your website’s page load time: You want your website to be quick and responsive in its performance to boost your user experience. The more responsive, the better as it’ll minimize your bounce rate. Run your website through PageSpeed Insights to start.
  • Optimize for multiple formats: Make sure you’re including multiple ad formats (sizes) to render properly on all kinds of devices.
  • Limit how often your ads refresh: Your ad refresh rate is directly related to your ad fill rate. This is because a higher refresh rate can contribute to latency, as well as lost impressions. By limiting your ad refresh rate to at least 30s, you’ll increase both your ad fill rate and your CPMs. Thus, making your ad inventory more desirable to demand partners and advertisers.

In summary

Your ad fill rate represents how many of your ad units were served out of all the ads requests sent to an ad server. It’s calculated by taking your total ad impressions and dividing them by the total number of ad requests. There are 6 main reasons why your ad fill rate may not be 100%.

  1. Technical errors
  2. Lack of demand
  3. Compatibility
  4. Latency
  5. Reporting discrepancies
  6. Adblockers

While some of these factors may be out of your control, there are still optimization opportunities that you can implement. Let us know if these optimizations helped to increase your ad fill rates.

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