Differences between AdWords and third-party data

Advertisers often notice two kinds of differences between the data in their AdWords accounts and those in their web server logs or third-party tracking software. One type occurs when your AdWords statistics show more overall clicks than your logs or tracking software report. The other occurs when your AdWords account shows fewer overall clicks.

While these discrepancies may be significant and at times surprising, they don't necessarily mean that there was some sort of invalid activity with your ads. We'll look at some common reasons for these discrepancies and offer tips to help you accurately track your clicks.

Reasons that your AdWords account may show more overall clicks

We've found that most discrepancies between your AdWords statistics and your web logs or third-party tracking software occur because third-party tracking methods are unable to detect all the clicks that your ads receive. There are several reasons for this:

  • Repeat clicks: Customers may click your ad several times when, for instance, comparison shopping or conducting research. Your third-party tracking software may not count these repeat visits to your site. As long as the click patterns don't fit a profile of abuse or invalid activity, however, they'll be counted in your AdWords account statistics.
  • Google Network statistics: Google displays ads on a growing network of search and content sites and products. Typically, web tracking software isn't able to recognize clicks from Google Network sites as being affiliated with Google. These clicks are generally labeled only with the third-party site name. If your ads are currently, or have ever been, distributed to Google Network sites such as About.com, AOL, Netscape, and others, we recommend using referrer headers and tracking URLs to monitor where your website visits originate.
  • Browser limitations: There are limitations to your third-party tracking software's ability to track website visits with referrer headers. Most of the newer Internet browsers automatically pass along a referrer header when a customer clicks your ad and is brought to your site. However, some customers deactivate this feature in their browsers. Also, some proxies and corporate firewalls strip out the referrer headers.
  • JavaScript not enabled: If your third-party tracking software uses cookies to record referrer headers, ad clicks that occur in a browser without JavaScript enabled won't be tracked. Your AdWords account, on the other hand, will record clicks that occur in browsers with or without JavaScript enabled.
  • Redirects: Redirects in landing pages can often prevent tracking code from launching and might prevent your third-party tracking solution from properly identifying and counting clicks on your ads.

Reasons why your AdWords account may show fewer overall clicks

Occasionally your AdWords account may show fewer clicks than your web logs. Here are some explanations for this mismatch:

  • Filtered clicks: Google's click protection technology may have automatically filtered out clicks that we determined to be invalid and prevented them from being charged to your account. You can see data on the invalid clicks that are automatically filtered from your account or specific campaigns.
  • Repeat visits: A customer might -- after clicking on your ad -- visit another link within your website and then hit the browser's back button. She might also bookmark the landing page and later return to your website directly through this bookmark. In both cases, the landing page will be reloaded and the third-party tracking software might count those as additional clicks.

Increase your tracking accuracy with Google Analytics

To accurately track traffic to your ads, we recommend using Google Analytics, a free, comprehensive tracking tool. Advertisers who create a Google Analytics account automatically enable a useful feature called "auto-tagging." Auto-tagging appends a unique identifier to an ad's destination URL each time it's clicked, which makes it much easier to distinguish real ad clicks from misleading behaviors such as page reloads. Google charges at most once for each unique tag (if we determine that the click is valid).