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How to Reduce Unfilled Impressions in Google Ad Manager

Unfilled impressions in Google Ad Manager mean loss of revenue. Meaning, publishers might have the ad space, but may not get ads or impressions for them. This happens mostly when some part of the inventory remains unsold. Or, some error prevents impressions from getting counted.

Most publishers experience some of their ad impressions showing up as blanks. In fact, about 10 to 15% unfilled impressions is considered as an acceptable rate. However, with the right measures and practices in place, it is possible to bring the rate down to as low as 3 to 5%. But to do that, it’s important to first understand the reasons that lead to unfilled impressions.

Once the reasons are caught, the next steps should be to find them (where Ad Manager comes in), and finally eliminate them. What’s the way of doing it? Let’s begin with understanding about unfilled impressions, and see how publishers can effectively deal with them.

What are Unfilled Impressions in GAM?

Ad networks and exchanges record the count of ads that fill up publishers’ inventories. For AdSense publishers, Google Ad Manager does that work. In the case when Ad Manager (or the ad network/exchange) is unable to find any ad to fill up the inventory, it is considered as an unfilled impression.

Why does this happen? This happens when both the ad network and the demand partner are unable to find suitable impressions for the advertiser and header bidding (auction for the ad impressions) is unable to take place.

Consequently, the ad server sends back a ‘blank impression’ to Ad Manager which gets counted as an unfilled impression. Simply put, an unfilled impression or a blank impression is an ad call which returned without an ad because no impressions were found eligible to serve.

Reasons for Unfilled Impressions in Google Ad Manager

There are a variety of factors that can lead to unfilled impressions一from technical issues to ignorance on the part of the publisher. Understanding the reasons why inventory goes unsold can help you minimise risk. Here are a few common reasons for unfilled impressions.

  1. Supply-demand balance:

    Sometimes, the publishers are at fault. They add too many ad units on their websites in the hope to get higher revenue through extra impressions. The result? Supply outstrips demand and impressions go unsold.

  2. Ad slot-request ratio:

    Similar to the point above, sometimes the header of the GPT (Google Publisher Tag) tag recognizes a high number of ad slots. But on the contrary, the number of ad display calls are too little to meet the supply. Here, having SRA (single request architecture) also factors in.

  3. No fallback ad network:

    Ad networks play a significant role in demand generation for publishers; if direct ad sales between publishers and advertisers does not work out. Hence, not having a fallback ad network configured could lead to unfilled impressions.

  4. Low ad viewability:

    Viewability is one of the most significant factors in measuring ad impressions and their value, with many networks and exchanges using it as a metric. Ad slots or ad inventory with less than 50% viewability may be at higher risk of being undersold.

  5. Ineffective setup or configuration:

    5. During setup, one common mistake many publishers make is not placing house ads to fill any remnant inventory. Moreover, improper setup of line items can also be a possible reason of unfilled impressions (more coming up on this later).

    It is important for publishers to have a general idea of each of the above reasons to understand their contribution in causing or worsening the incidence of unfilled impressions.

Finding Unfilled Impressions in Google Ad Manager

Once publishers have the reasons, detecting them is the next step to be able to deal with them. Here goes the steps to do that:

  1. Sign in to your Google Ad Manager account.
  2. Go to Reports > Queries > New query.
  3. Go to Edit and set a data range.
  4. Under Dimensions, type Ad unit (to see ad unit wise unfilled impressions) and Requested ad sizes (to see ad size wise unfilled impressions).
  5. Under Metrics, check mark the Unfilled impressions box.
  6. Hit Run.

reduce unfilled impressions in GAM
reduce unfilled impressions in GAM
find unfilled impressions in GAM

Once publishers have the report in hand, it is wise to save it and refer to the Ad unit and Ad request size section to find the location of the tags. This will help you figure out which ad types are reporting the maximum volume of unfilled impressions.

FYI, till June 2018, DFP and AdX were separate entities before they became an integrated product, Google Ad Manager. Back then, publishers used to refer to DFP to check reports like unfilled impressions. Now, that happens on Ad Manager.

Alternate Way to Find Unfilled Impressions

  1. Sign in to your Google Ad Manager account.
  2. In Home, scroll down to Top detected yield partners.
  3. Click the View in query tool option.
  4. Click Edit and follow the same steps under New query, as stated in the above section.
unfilled impressions in google ad manager
find unfilled impressions in google ad manager

Ad Manager gives the option to see level-wise reports. While the above method allows publishers to see direct reports, the other way of reporting looks like this:

In this method, sometimes the unfilled impressions checkbox may not be selectable. Here, the condition is that publishers need to integrate ‘demand partners’ as ‘yield partners’ for the data to get fetched in the report.

In addition, just like the first method, this report also gives publishers the insights they need to find the ad types which witness the most unfilled impressions. As a practice, publishers should also check the average ads per page, i.e., total number of impressions / total number of page views. If the resulting number is small, it is an indication of unfilled impressions.

How to Reduce Unfilled Impressions

#1 Remove some ad slots: The first thing to look at is the report fetched via Ad Manager一Ad unit and Ad request sizes. The ideal step? Eliminate the highlighted ad spaces from the webpage by referring to tag placement insights.

#2 Header bidding: Currently, header bidding is the most relied upon way for publishers to generate demand. The right header bidding partners helps increase ad fill rate and CPMs for increasing competition for the inventory.

#3 Inventory segmentation: Segment the ad inventory to get more third-party demand partners. Segmentation allows a part of the inventory to be targeted to specific geographies, networks, etc. this helps get higher chances of filled inventory. Also, try to set a frequency cap on line items to maximise the fill rate from third-party partners.

#4 Viewability and auto-refresh ads: Compromised ad viewability and poor implementation of auto-refresh ads often leads to unfilled impressions. Make sure that viewability standards are met and there’s a decent time gap between auto-refresh ads (ideally, between 30 to 60 seconds depending on the average session duration of a website).

#5 Ad placement: In the ‘reasons of unfilled impressions’ section, the first point stated that publishers create too many ad slots, which reduces demand. Rather that doing that, publishers should be mindful and experiment with ad placements, e.g. replacing non-standard small ad units with standard larger ad units, instead of increasing the number of ads.

Moreover, if you noticed, a few reasons for unfilled impressions stated about certain things that publishers ‘don’t do’, e.g. not having an ad network or not placing house ads. Therefore, in order to deal with unfilled impressions, the plan of action should be to do the opposite一sign up with a decent ad network and place house ads to fill remnant inventory.

Address Problems with Line Items

Inactive line items is one of the root causes of unfilled impressions. Many of the reasons are directly or indirectly related to line items. Hence, the next step should be to find line items which do not serve any ads. Here’s how to do it:

  1. Sign in to your Google Ad Manager account.
  2. Click Delivery > Line items.
  3. Apply Filters to find specific line items and refer to the ‘status’ of the line item.

Depending on the status of the line item viz. draft/inactive, ready, or delivering, the actions might vary. Once line items are fixed, it would make sense to implement proper targeting methods by enabling ad targeting based on device, connection, key value, geography; and others, if applicable.

Also, there are Ad Manager delivery tools which can help publishers understand why line items might not be functioning. In the case where no line items cater to ad spaces, that means there are going to be unfilled impressions.

Final Word

Apart from the reasons explained above, there are some everyday factors that may, or may not, lead to unfilled impressions, but are worth observing. These include:

  • High CPM floors which affect advertisers’ purchase behavior towards the inventory.
  • Inadequate demand to monetize impressions due to non-English geographical traffic.
  • Slow page load time disrupting the ad renderings in a given user session.
  • Blank ads and discrepancies in reporting made from the ad networks’ end.

The issue of unfilled impressions is probably everlasting. So the industry accepts it up to some extent (10-15%). However, platforms like Google Ad Manager give publishers the control to take necessary corrective actions. Therefore, it is doable to reduce unfilled impressions, even for publishers with little technical knowledge or developer skills, if done right.


1. How do you fill unfilled impressions?

Set a data range in Edit. Under Dimensions, select Ad unit (to see unfilled impressions by ad unit) and Requested ad sizes (to see unfilled impressions by ad size). Check the Unfilled impressions box under Metrics. Press the Run button.

2. How does Google Ad Manager count impressions?

Google Ad Manager counts mobile app impressions in accordance with industry standards. The impression of a mobile app occurs when one or more pixels of the ad creative are visible on the device’s screen. Currently, this methodology is used by Ad Exchange creatives, some Ad Manager creative formats, and Open Bidding.

3. What causes impressions to decrease?

A competitor’s new account or an adjustment to their existing account can have an impact on how many impressions your ads receive. For example, your biggest competitor might raise their bids, pushing your ad off the first page. Impression numbers may then decrease.

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