What is Ad Fill Rate and How To Optimize it

In web monetization, there are many numbers you need to be constantly aware of. Ad Fill Rate is one of them. But what does it stand for? What determines it? How can you optimize your fill rate and is it supposed to be 100%? Read below to find out the answers to these questions and more. 

What is Ad fill rate?

The fill rate represents the ratio between the number of successfully delivered ads versus the number of ad calls made. Or, to put it simply, fill rate is the percentage of ad calls that resulted in a filled ad spot.

How do you calculate it?

You can calculate your fill rate as follows: Divide the number of ads served by the total number of ad requests. Then, multiply by 100 to get a percentage. So for example, if 60,000 ads were delivered out of 100,000 ad calls, that gives you a 60% fill rate.

Should you aim for a 100% fill rate?

As you’re probably aware, reaching a 100% fill rate is almost impossible. But should you actually strive to achieve a perfect fill rate? Not really. Your fill rate is just one of the indicators of monetization success – and a high fill rate doesn’t always mean higher revenues. Usually, as the fill rate increases past a certain point, CPM rates will decrease. After your premium ad inventory is filled with top-paying ads, the remnant inventory that’s left will generally be filled at progressively lower rates.

It’s best to think of it this way: You should aim to achieve the best balance between CPM and fill rate. That is, you and your ad monetization partners should tweak your target CPMs and fill rate to avoid a drop in overall ad revenue.

Why isn’t it 100%?

There are several factors that make achieving a perfect fill rate difficult. Let us take a look at the most common ones below.

  • Technical errors

No technology is immune to technical errors and that applies in full force to online advertising. There is a long chain of events before an ad is served. So whether it’s communication issues, multiple verification steps, or lack of ad ops expertise, technical problems could contribute to decreased fill rates.

  • High competition or low demand

Working in a popular field with lots of competition or a very niche field can both hurt your fill rate. In the first case, that’s due to a large amount of inventory available on the market. The second, your chosen ad network may not have sufficient demand for your niche. 

  • Latency 

Page latency is the delay between the request and the display of the content or ad. It leads to a negative user experience and bad stats. Your users may leave the page before the ad has had the chance to load. This will deter advertisers and hurt your fill rates and revenue. 

  • Compatibility issues

With the rise of mobile, publishers need to act accordingly. If you don’t have mobile-friendly ad units, you could be missing out on available demand.

  • Reporting discrepancies

Different platforms often use different metrics and tools to count ad impressions. For example, your ad server counts all ad calls sent out. However, demand providers only count ads served. In the end, it leaves publishers comparing apples to oranges.

  • Ad blockers

Some adblockers block ad networks instead of ad calls. So while an ad call is still generated, the ad blocker then hinders ad delivery, leading to lower fill rates. 

How to solve issues and optimize fill

  • Choose a strong monetization partner

Supply-side platforms differ in the demand and rates they can offer. For example, they may focus on particular geos or tiers. Thus, it’s important to find the right monetization solution or combination of solutions. Don’t be afraid to experiment to determine what fits your needs.

  • Set up price floors

Setting up price floors can be the key to achieving the best balance between CPM and fill that we mentioned above. But if they’re too high, you may lose bids. If they’re too low, you may undervalue your inventory. So, you can experiment with dynamic floor pricing which adjusts automatically based on historical bid data. Or you can create line items with different price floors. Your ad monetization partner can always guide you in the process.  

  • Improve page speed

There are various ways to improve page loading times. Some techniques include minimizing HTTP requests, using a CDN (Content Delivery Network), optimizing image size, etc. Others have to do with ad serving. They include setting an auction timeout for your header bidding partners, carefully managing your waterfall, etc.

  • Make up for ad blockers

There’s a way to calculate how much damage ad blockers are causing. If you’ve already measured your ad-blocked traffic, check out BlockThrough’s Adblock Revenue Recovery Estimator to get an estimate on how much more revenue you would be making. Then, there are several ways to try and offset adblocking. For example, you can adopt the ‘Acceptable Ads Standards’. They indicate what ads are deemed non-intrusive and therefore, ‘acceptable’, and can be delivered to ad-blocking users. As long as they consent, of course. Another approach is to use Server-side ad insertion to stop video ads from being blocked. 

  • Optimize ad sizes and ad placements

To ensure you accommodate more demand, opt for popular and innovative ad formats. You can use responsive ad formats to cater to different devices and operating systems, e.g. mobile, tablet, etc. Analyze how users interact with your website to place ads so as to ensure good viewability.

Wrap Up

This concludes our list of factors affecting fill rate and the ways to optimize it. It’s by no means exhaustive. However, we hope it can direct your attention to common issues. While it doesn’t need to be 100%, fill rate cannot be neglected. So whatever problems you’re facing, good analysis, adequate measures, and strong support from your ad monetization partner can help.