Third-party discrepancies
When an ad server delivers line items that are hosted by a third party, reporting discrepancies between the two systems will occur, and it is common to see campaign variances of up to 20%. Check the lists in "More about third-party discrepancies," below, to learn why discrepancies may occur and what you can do to prevent them.
Discrepancies may result from:
Latency: Lag between an initial line item request and the appearance of the creative can lead to differences in counts. For instance, a user will often navigate away after the browser receives the DFP line item request but before the third party responds with the requested line item, or a user may click on a link but navigate elsewhere before the landing page has loaded.
Network connection and server reliability: A third-party ad server may fail briefly or encounter an issue that prevents it from logging an impression.
Ad blockers: Ad blocking software can prevent the line item from being delivered by the third party after DFP has already counted an impression.
Low impression goals: A small numerical discrepancy can cause a high percentage discrepancy if the line item delivered few total impressions. For example, if you have a campaign delivering 100 impressions per day, a single-day discrepancy of 30 impressions will lead to a single-day discrepancy of 30% even though the actual number of missed impressions is low.
Tracking methodologies: DFP counts line items requests, but a third party may record an impression at a different time (e.g., when a tracking pixel is rendered).
Filtering: Ad servers have different methods for filtering impressions from spammers, bots, spiders, back-to-back clicks, link analyzers, and other automated or non-representative web traffic.
Things to check:
1. Are macros implemented properly?
2. If DFP recognizes the third-party ad server you are using, let it automatically insert the macros. If you are unsure of where to place macros, talk to your creative developer, advertiser, or third party for guidance.
3. %%CACHEBUSTER%% -- Make sure there's a random number properly inserted in each call.
4. %%CLICK_URL_ESC_ESC%% or %%CLICK_URL_UNESC%% -- Verify that the click macro is included in the correct portion of the click-through URL in your code.
5. %%VIEW_URL_ESC%% or %%VIEW_URL_UNESC%% -- For interstitial creatives, ensure that this macro is included in your creative's code.
6. As a best practice, we recommend using an unescaped (...UNESC) click macro when the creative hosted by another server is a standard image file such as a GIF or JPEG. You should use the double-escaped (...ESC_ESC) click macro for Flash creatives and certain third parties.
7. If you are using Google Publisher Tags (GPT), have you defined more ad tags in the webpage header than you display in the body section of your webpage? Ad tags that are defined in the header but not displayed in the body will be counted as impressions whenever the tag is loaded, but they won't make calls to third-party servers. That will lead to discrepancies. Make sure that all ad tags defined in the header are also displayed in the body of the webpage.
8. Are you comparing the same date range across the third party and publisher?
Do both DFP and the third party use the same time zone? Ad servers that report based on different time zones will return different results.
9. Are you comparing the same line items/ads?
10. Do you use the same third-party tags in any other line items in your network?
11. Did you confirm with the third party that the same tags have not been provided to any other publishers?
12. How large is the creative asset? Large creatives can have long load times and can cause differences in impression count timing.
13. Does the DFP report include unfilled impressions? Unfilled impressions will inflate DFP’s numbers by including instances where the third-party ad server was not called.
14. Is the line item using geographic targeting on the third-party ad server? Different ad servers map IP address location data differently, leading to significant discrepancies.
Is the line item day- or time-parted on the third-party ad server? Day- or time-parting on the third-party ad server can lead to DFP counting impressions in situations where the third party does not return a line item.
15. Does the creative require calls to multiple third-party ad servers (also known as "daisy-chaining")? Each third-party ad server can lead to campaign variances of up to 20%. If one third-party server points to yet another third-party server, the expected discrepancy increases. (With 80% accuracy between each server, this results in a normal discrepancy of up to 36%, as shown in the following calculation: 1 - (1 - 0.2) × (1 - 0.2) = 0.36).
16. Does the third-party ad server use frequency capping? A third-party frequency cap will prevent an ad request from being filled despite the fact that DFP has counted an impression.
Source: Google support
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