How to investigate discrepancies – DoubleClick

The best practice is to always traffic DFA tags using the "DoubleClick tag" creative type. If you have trafficked, your DFA tags as a DoubleClick tag creative type and are experiencing a discrepancy of greater than 2%.

Normally, DFP records an impression as soon as the ad server determines which creative to send. When the DoubleClick tag creative type is chosen, however, DFP does not record the impression until the line item has been sent and an impression has been recorded by DFA. As a result, this process reduces discrepancies between DFP and DFA, typically to within 2%. The DoubleClick tag creative type will also eliminate the need to add click tracking macros.

If a DoubleClick tag is booked as a custom or third-party creative, this enhanced functionality is lost; DFP will treat the DoubleClick tag as a third-party tag. It will not report clicks without the DFP click macro, and you will see a larger discrepancy in delivery numbers (as you would with any third-party ad server). If you have trafficked DoubleClick tag as a custom or third-party creative type and are experiencing a reporting discrepancy between DFP and DoubleClick for Advertisers (DFA), please see the “Third-party discrepancies” article. Otherwise, explore the following possibilities.

Discrepancies may result from:

Invalid activity filtering: DFP and DFA differ slightly in filtration methodologies, which can result in discrepancies in instances when frequent invalid activities occur.

Things to check:

• Has the correct DoubleClick tag been trafficked? Like DFP, DFA has many tag types, including one that is specifically intended for use in DFP.
• Are you comparing the correct objects between DFA and DFP? Which DFA ads are included in the placement for the tag you’ve trafficked in DFP?
• Have you or the advertiser made any changes during the time in question (e.g., reassigning or modifying creatives)?
• Are you looking at daily data or aggregated results? Break out the data by day and line item.
• Does the advertiser code load properly? Perform live tests on web pages where the line item should deliver to verify that the correct ad tag calls are being made.

Source: Google Support

How to investigate discrepancies – Analytics

Analytics packages (such as Google Analytics) measure different metrics than ad servers, so their reports will not reconcile with DFP.

Page views vs. impressions

Analytics tracking is based on page views. In contrast, DFP ad server concepts are, by design, not page-specific:

• An ad tag can be placed on multiple pages.
• An ad unit can be associated with many pages.
• A line item can be targeted to multiple ad units.
• A line item can serve to a single page multiple times.

Code execution

DFP counts impressions delivered to ad tags; analytics packages count the execution of analytics tracking code. Since these snippets of code are located in different parts of your page code, both scripts might not load or execute on every page view.

For instance, some analytics packages recommend placing tracking code at the bottom of your HTML. If a user exits a page before the tracking code is executed, the analytics package will not count a page view, but DFP will still count an impression.

Since there is no interaction between ad tag code and analytics tracking code, analytics packages cannot account for unfilled impressions, which can be caused by any number of variables:

• A lack of inventory
• Firewalls and misconfigured security software
• Ad blockers
• Intermittent network connections
• General latency

Iframes

Some publishers serve DFP tags in iframes. Browsers that don't support the <iframe> tag will not report an impression, but an analytics package will count a page view. Ad tags within an iframe can result in an extra round trip between the browser and server. This additional latency can cause some users to leave the page before the browser has enough time to make the calls to both the analytics package and DFP. If the analytics tracking code is present within both an iframe as well as the parent frame, the analytics software will register an inflated number of page views.

Cookies

Analytics packages typically require cookies to track page views. Some packages only record visitor traffic associated with a visitor cookie. If this cookie information is not available for a hit, or if a user has disabled cookies, then that hit may be disregarded.

Referrers

Comparing referrer URLs to DFP clicks is not advised. Referrers in analytics are not an accurate measure of clicks or landings for the following reasons:

• Referrers can be disabled by users.
• Internet security applications can block referrer data.
• Firewalls and proxy servers can filter referrers.
• Users can spoof referrers to prevent servers from knowing where they've been.
• Depending on the line creative type (rich media, standard image, etc.) and the ad tag (iframe, JavaScript, standard HTML, etc.) on the page, the referrer can be either “DoubleClick” or your domain.
• Internet Explorer does not send referrer data when switching from either (a) HTTP to HTTPS, or (b) any non-HTTP/HTTPS protocol (e.g., file://) to HTTP/HTTPS.

Source: Google Support