8 Ways To Investigate Impression Discrepancies

Posted by Tim Nichols

Apr 23, 2014 5:11:00 PM

Despite best efforts, discrepancies in statistics are still quite a big issue for advertisers and publishers investigate_impression_discrepanciesor between the advertiser’s statistics and the advertising platform's statistics. Typically, discrepancies of up to 10% can be acceptable; however, at times they can reach 20% and more. There are many different reasons why discrepancies occur. For example, counting methodologies can differ between parties, as each party can potentially count an impression at a slightly different point in the delivery of an ad (i.e. publishers can count impressions at the time the ad request is sent, while advertisers can count an impression when the creative/ad is delivered).

One thing to take into consideration is that before investigating any discrepancies always ask for most granular 3rd party report (e.g. hourly or at least daily). If discrepancies occur very suddenly, always check if anything was changed in campaign setup, (e.g. new creative added, new inventory sources added etc.).

Also, before you can begin to investigate be sure to gather the correct reports from each system. This will allow you to first confirm a discrepancy is present and will ensure further investigation is done on the appropriate data sets. To do so, collect the following: 

  • Two reports: one pulled from ExactDrive reporting and one pulled from your third-party tracking system.
  • Both reports must contain data from the same time frame.  The more granular time frame provided (month, week, day, or hour) the better .
  • Both reports must contain data from within the same time zone.  The time zone must be specified on both reports.
  • The objects for which you are pulling data (campaign, placement, advertiser, etc.) must be specified in both reports.
  • Objects in the third party report (campaigns, placement, advertiser, etc.) must correspond with objects in the ExactDrive system.  The ExactDrive IDs of these objects must be noted in the report so that we can compare to numbers from ExactDrive reporting.

If these reports have been collected and a discrepancy has been confirmed review the following list of common causes to try to isolate the issue. 


1.) Time difference (different time zones)

One of the most common reasons for discrepancies is that reports from different platforms are in different times zones, (e.g. one platform uses ET, while another uses UTC). Make sure time zones match in all reports before starting to compare statistics.

2.) Different counting technologies

As mentioned above it’s quite a common issue that each party counts an impression at a slightly different point in the delivery of an ad, (e.g. publishers count at the ad request, advertisers count when the ad is delivered). In general it shouldn’t cause big discrepancies as if ad request is sent in most cases ad will be delivered just fine, however it’s possible that browser crashes, user closes a browser or navigates to another page thus impression is not counted in 3rd party ad server.

3.) Intermediaries (e.g. Integral Ad Science, Pixalate)

If there are any intermediaries used in ad delivery process then it causes recorded impression discrepancies as well. For instance, let’s say Pixalate is used to block ad delivery on blacklisted domains then it is possible that the ad request is sent, but ad delivery is blocked. Once again it shouldn’t cause huge discrepancies as the number of impressions on blacklisted domains is usually really small, but it’s worth checking this when investigating recorded impression discrepancies.

4.) Missing cache buster

Caching is a technique of storing content locally on a viewer’s computer that is commonly used by web browsers to improve the overall speed and performance of loading web pages. If caching is enabled in a viewer’s browser (enabled by default on all major browsers), the browser will save images and other page elements to their computer the first time that a web page is visited. The next time that the same page is visited, the browser will load the images and elements saved locally on the viewer’s computer instead of pulling the content directly from the original server.

With ExactDrive, caching can lead to impression discrepancies when dealing with externally hosted creatives. If a third-party URL or ad tag is saved on a viewer's computer the first time that the ad is seen, then by default the ad will subsequently be pulled from the viewer's cache. Consequently, these ad impressions will not be tracked, which may cause impressions reported in ExactDrive to be significantly higher than impressions recorded in an advertiser system.

cachebuster is a dynamic value that can be inserted into a third-party ad tag or URL at runtime in order to force each ad call to be unique. This ensures that the ad is pulled from the advertiser ad serving system every time so that impressions will be tracked properly. In order for this to be the case, when a third-party creative is uploaded into ExactDrive, it is necessary to insert the ${CACHEBUSTER} macro in each place in the creative where a dynamic value should be populated at runtime. Not including the ${CACHEBUSTER} macro in third-party creatives is the most common cause of impression discrepancies.

How To Resolve

Ensure that your third-party ad tags or URLs in ExactDrive have the ${CACHEBUSTER} macro inserted properly. The exact location(s) for where to insert the macro in each creative varies depending on the ad server.

The cachebuster is intended to make a URL call unique. Thus, even if an ad server doesn't provide a specific location for a cachebuster to be inserted, it can always be inserted manually. In the example below, the cachebuster is inserted at the end of the URL:

<a href="http://ad.doubleclick.net/jump/1234.567.890/;net=123456;sz=728x90?cb=${CACHEBUSTER}" target="_blank">

<img src="http://ad.doubleclick.net/ad/1234.567.890/;net=123456;sz=728x90?cb=${CACHEBUSTER}" width="728" height="90" border="0" alt="">


The cachebuster parameter name (in this case "cb") doesn't actually matter; it can be anything as long as it is not a reserved parameter of the third-party ad server (e.g. "click" for passing in a third-party click tracker).

5.) Impression Page Drop Off

A page drop off occurs when a viewer leaves a page prior to a creative being loaded or when something prevents the creative from loading completely, such as a loss of network connection or a crashed browser. A small amount of page drop off is normal due to typical page load issues and failed requests. Discrepancies that are caused by this issue typically occur when a creative is loaded into a placement at the bottom of a page and is therefore loaded at the end in the normal chain of page load events.

How To Resolve

Generate a domain level report for the affected campaigns then check for domains where a significant amount of impressions have been served and visit the webpage of each domain fitting this criteria. If the page takes longer than a few seconds to load completely, a slow web server could be causing the discrepancy.

The most likely scenario in this case is that ExactDrive is delivering the creative content and recording an impression, but the content isn't being loaded from the ad server. Consequently, the ad server isn't recording an impression. If it is determined that a discrepancy is caused by slow page load and drop off, we recommend that you follow these steps:

  • Add the domain to a campaign or blacklist
  • Escalate the information to the ExactDrive customer support team

Please note: Not all publishers or inventory partners choose to expose their domains during reselling. As a result, a site domain not present in reporting may be causing the discrepancy. If there is a discrepancy issue present, and there is a publisher/website combination where a significant amount of impressions are being served, please escalate the issue to the ExactDrive customer support team for further investigation.

6.) Heavy creatives

If creative is heavy then it can take more time to load it from 3rd party ad server. The problem here is that while such ad is loading user can close a browser or navigate to another page. This shouldn’t be a common issue, however always check how heavy the creative is that’s being hosted by a 3rd party ad server and if possible check how long it take for the creative to load.

7.) Creative Type

Make sure that the creatives are properly configured. For instance, that HTML creatives are not set up as JavaScript type. Breaking out an impression report by creative should be very helpful in exposing potentially problematic creatives. Make sure on the Third-party impression tracking pixels that the format type matches the content of the pixel, (i.e. Both JavaScript or both HTML).

8.) Geo Mapping Mismatch

Differences in how geo mapping is determined may cause mismatches. ExactDrive uses Media Mind (now Sizmek) for geo mapping.  It is possible our IP mapping might be different then the 3rd Party ad server being used by the advertiser.

Topics: Media Buying & Planning, Reporting & Analytics, Online Advertising, Impression Discrepancies

Our self-serve advertising platform with managed services provides a leading solution for advertising your brand online.

Test Drive It

Receive Updates

Posts by Topic

View All >