Ad Fill Rate Explained: How to Maximize Revenue for Your App or Website

When it comes to making money from your mobile app or website, one thing that can make or break your revenue is your ad fill rate. This key metric determines how efficiently your available ad inventory is being utilized.

A low fill rate means advertisers aren’t bidding on your inventory as much as they could be, while a high fill rate ensures you’re maximizing every impression.

So, what affects fill rates? And more importantly—how can you improve them to boost your revenue? Let’s break it down.

What is Ad Fill Rate?

Ad fill rate is the percentage of ad requests that successfully turn into actual ads being shown. It’s calculated like this:

Ad Fill Rate (%) =

Ad Impressions Served Ad Requests Made

× 100

For example, if your app or website sends 1,000 ad requests and receives 900 ad impressions, the fill rate is 90%. This metric indicates how efficiently your ad partners or mediation platforms fill your available ad inventory.

What Affects Your Ad Fill Rate?

Several factors affect ad fill rates for both apps and websites:

1. Where Your Audience Is (Geographical Demand): Advertisers don’t value all regions equally. Some areas have high advertiser demand, which means better fill rates and higher CPMs (cost per mille). Other areas may not attract as much interest from advertisers, leading to lower fill rates.

2. Ad Format Matters: Not all ad formats perform the same way. For example-

-Rewarded video ads work great in gaming apps but not as well on news websites.
-Banner ads might do well on a website but could be ignored in an app.

3. User Internet Connectivity: If users have a slow or unstable internet connection, ads might not load properly, which lowers your fill rate. This is especially common on mobile networks. To combat this, publishers should optimize ad delivery for low-bandwidth environments.

4. Technical Issues: Sometimes, the problem isn’t with demand but with how ads are being served. Issues like:

-Incorrect SDK integration in apps
-Improper ad tag placement on websites
-Latency issues with ad servers

All of these can prevent ads from being delivered properly. Regular technical audits help ensure everything runs smoothly.

5. Inventory Quality (What’s on Your Site/App?): The quality of your content and ad placements matters. Advertisers prefer ads that are viewable (actually seen by users) and placed alongside relevant, engaging content. If your content is low-quality, advertisers may bid less or avoid it altogether.

6. Too Many Ads Can Hurt You: It’s tempting to cram as many ads as possible onto a page or screen to increase revenue. But too many ads can ruin the user experience, leading to lower engagement, ad blocking, and even fewer ad impressions in the long run. Finding the right balance is key.

7. Your Partnerships Matter: Who you work with—ad networks, DSPs (demand-side platforms), and mediation partners—also affects your fill rate. Having access to a variety of advertisers increases competition, which improves fill rates and revenue. If you rely on just one or two ad networks, you’re at the mercy of their demand fluctuations.

8. Seasonality and Trends: Advertiser demand changes throughout the year. For example, demand spikes during the holiday season when brands ramp up their ad spend. Staying aware of seasonal trends can help you adjust your monetization strategy at the right time.

How to Improve Your Ad Fill Rate

To boost fill rates across apps and websites:

1. Integrate Multiple Demand Sources:

Don’t put all your eggs in one basket. A mediation platform lets you access multiple ad networks, increasing your chances of filling ad requests.

2. Optimize Ad Placements:

Strategically place ads in high-visibility areas without compromising user experience. For apps, consider in-app placements like between game levels; for websites, above-the-fold placements often perform better.

3. Perform Regular Technical Audits:

Ensure proper SDK integration for apps and validate ad tags on websites to avoid missed opportunities.

4. Adjust for Geo-Targeting:

If certain regions have consistently low fill rates, consider adjusting your targeting or working with regional ad networks.

5. Implement Ad Refresh Strategies:

For both apps and websites, refreshing ads at suitable intervals can increase fill rates without overwhelming users.

The Sweet Spot: Balancing Fill Rate and Revenue

It might seem like the goal should be a 100% fill rate, but that’s not necessarily the best strategy. Filling every ad request with the lowest-paying ads could actually lower your overall revenue.

Instead, the goal should be to find the sweet spot:

-A high fill rate (so you’re not wasting ad inventory)

-Strong eCPMs (so you’re making good money per impression)

To achieve this, work with premium ad networks that offer both a high fill rate and competitive eCPMs. This way, you’re not just showing more ads—you’re showing the right ads that generate the most revenue.