Industry standards for measuring clicks

MRC logo The Media Rating Council (MRC) accreditation certifies that Google's click measurement technology adheres to the industry standards for counting interactive advertising clicks and that its processes supporting this technology are accurate. This applies to Google’s click measurement technology, which is used across all device types (desktop, mobile, tablet) in both browser and mobile apps environments.

The industry guidelines were developed in an effort coordinated by the Interactive Advertising Bureau (IAB) and the MRC to govern how interactive advertising clicks are counted and how invalid clicks are detected and handled. The audit against these guidelines was conducted by a CPA firm engaged by the MRC to perform the audit.

You'll find a summary below of the click measurement process employed by Google AdWords and AdSense. For additional resources, please visit IAB/MRC Click Measurement Guidelines. (The guidelines provide a description of the IAB standards for counting online ad clicks.) You can also view Google’s accreditation letter.

What is included in the audit process

This audit is focused on Google's pay-per-click advertising systems. Google provides advertiser-facing pay-per-click solutions through "AdWords" and publisher-facing pay-per-click solutions through "AdSense". While AdWords Express was included in the most recent audit, and consideration of it by MRC is currently in process, AdWords Express is not yet accredited by the MRC.

AdWords advertisements may be administered to users through the following products or services: AdSense for Content (AFC), AdSense for Domains (AFD), AdSense for Search (AFS), Doubleclick Ad Exchange (AdX) and AFC relates to advertisements displayed on the pages of a partner site, where the context of the information on the page is used to determine and display relevant advertisements. AFD relates to advertisements displayed on the pages of a particular domain, where the domain name itself is analogous to a search query. AdX relates to advertisements displayed on participating partner sites, where the context of the page and real-time bidding is used to determine and display relevant advertisements. AFS and relate to advertisements displayed as paid results within the context of search engine query and results.

What is not included in the audit process

Google's impression-based advertising solutions, such as DoubleClick, and systems which measure clicks for non-commercial purposes (such as Google search) are outside the scope of this audit. Other systems outside the scope of this audit include related support and management systems such as Google Analytics.  

Click measurement methodology

The measurement methodology is based on all click activity recorded, and does not utilise sampling for the purposes of click measurement. Only stage 2.2 of the IAB click referral cycle (measured clicks) are directly observed by Google. With respect to the click-referral cycle, upon receipt of the initial click transaction by the AdWords redirect server, AdWords records the click and issues a non-cachable HTTP 302 redirect to the browser based on the location established by the Advertisers for the specific advertisement. This constitutes the measured click. The click measurement methodology is the same across all device types (desktop, mobile, tablet) and for browser and mobile apps, unless otherwise noted.

Ads can be displayed on mobile devices that are supported by the Google Mobile Ads SDK (see here for list of currently supported platforms). AdWords Express does not support serving ads in mobile apps.

A known limitation of this method of measuring clicks is that a network interruption may cause a user who successfully receives a 302 redirect to not be able to view the resulting advertiser website.

The counting methodology utilised is the multiple-click-per-impression method. Consequently, to avoid inappropriate counting of navigational mistakes (e.g. multiple clicks per user), we require that the time between a given click and a previous click on the ad impression is greater than a specific period of time.

Logs are generated and processed in real-time, storing all data associated with observed HTTP transactions. Numerous variable and heuristic techniques are utilised to implement the click filtration systems, which will not be enumerated here to protect their security.

Both Google and their partners deliver the advertisements to users; however, Google maintains control over and performs the processes related to measurement and advertiser reporting of click activity. When a user clicks an advertisement, whether delivered by Google or a partner, via any one of the products administering the ad, the click activity is tracked by AdWords through the AdWords redirect servers.

Measurement of click activity is based on the Google AdWords click measurement methodology, which utilises a technology infrastructure to manage and monitor click events. A click is recorded (measured) when AdWords has received an initiated click and sends the user an HTTP 302 redirect to the advertiser landing page or website (or other intermediate server such as an advertiser's agent). These measured click events are recorded to data logs within an event file system. The data log files are then accumulated, edited and compiled through fully automated processes to produce click measurement and advertiser reporting. The editing process includes the process of filtering erroneous or corrupt data, identified non-human traffic including robots and other automated processes, and other identified invalid click activity. The filtered clicks are considered invalid, which means they are not billable to the advertiser. Google prepares click reports for advertisers which can be directly accessed by the respective advertiser.

Click measurements can be reported aggregated by geographical location (not subject to MRC accreditation) and device type. Geographical location is based on the user’s IP address or from a publisher-provided location (publishers must obtain user permission to provide such location). Note that some traffic may be routed through a service provider’s proxy servers and so might not correctly reflect the user’s actual locations (e.g. mobile carriers may proxy mobile traffic). Device type classification (computer, tablet and mobile devices) is based on information from the HTTP header-using libraries operated by Google.

In some AdSense implementations, partners render ads on their own site subject to their own design and formatting rules and control the clickable area around the ad. In these implementations, adjustment of this area is beyond Google's control. In regular AdSense implementations, Google both controls the clickable area as well as renders the ad impression directly to the end user.

Filtration methodology

Google tries to identify and filter both general and sophisticated invalid traffic continuously through data-based identifiers, activities and patterns. This includes non-human activity and suspected fraud. However, because user identification and intent cannot always be known or discerned by the publisher, advertiser or their respective agents, it is unlikely that all invalid traffic can be identified and excluded from the reported results proactively. In order to protect invalid traffic filtration processes from becoming compromised or reverse-engineered, no details of specific filtration procedures, beyond those detailed in the Click Guidelines, will be disclosed, other than to auditors as part of the audit process.

Both specific identification (including obeying robot instruction files, filtration lists and publisher test clicks) and activity-based filtration methods (including analysing multiple sequential activities, outlier activity, interaction attributes and other suspicious activity) are utilised in filtration.

In addition, the following parameters apply to the filtration methodology:

  • Third-party filtration is not used by Google.
  • Robot instruction files (robots.txt) are employed.
  • Sources used for identification of non-human activity: Google uses the IAB/ABCe International Spiders & Robots List, as well additional filters based on past robotic activities. The IAB Robots List exclude file is used.
  • Activity-based filtration processes: Activity-based identification involves conducting certain types of pattern analyses, looking for activity behaviour that is likely to identify non-human traffic. Google's Ad Traffic Quality team has systems in place to determine any suspicious activities and does such activity based filtering appropriately.
  • All filtration is performed 'after-the-fact' and passively. That is, the user (browser, robot, etc.) is provided with their request without indication that their traffic has been flagged, or will otherwise be filtered and removed as Google does not want to provide any indication to the user agent that their activity has triggered any of Google's filtering mechanisms.
  • Processes have been implemented to remove self-announced pre-fetch activity.
  • Processes are in place to allow publisher test clicks. These processes support publishers adding a specific tag to an ad request to indicate that the ad request is a test request and should not be counted for any billing or official accounting purposes.
  • When inconsistencies or mistakes are detected, processes exist to correct this data and provide refunds to advertisers. These refunds are reflected in the billing summaries. The corruption of log files is extremely rare, but in cases where this may occur, processes exist to recover them.
  • Processes have been implemented to remove activity from Google internal IP addresses.
  • Filtration rules and thresholds are monitored continuously. They can be changed manually, and are updated automatically on a regular basis.
Business partner qualification

All partners that display AdWords advertising on their content are required to adhere to our programme policies, which prohibit invalid activity. Learn more about invalid activity.

Google filters for invalid traffic on an ongoing basis, and will review any business partners that receive high amounts of invalid traffic. Partners who continually receive high amounts of invalid traffic may have their account suspended or closed.

Data reporting

AdWords reports the total number of clicks, the total number of impressions and subsets of this data (e.g., clicks, impressions, and clickthrough rates, by campaign, ad group and keyword) to advertisers, and similar data corresponding to site statistics to publishers. AdWords Express reports the total number of clicks, the total number of impressions and subsets of this data (e.g., clicks, impressions and clickthrough rates, by device and property) to advertisers. The scope of the audit process covers the click and advertiser reporting for AdWords and AdWords Express. These figures may fluctuate to an extent during the course of the month and are not considered finalised until they are frozen at month end. After this time, the reported clicks will not be adjusted, however, credits may be given to advertisers if Google deems it appropriate.

AdWords includes the capability for advertisers to see the total number of daily clicks filtered (marked invalid) for each campaign. AdWords doesn’t report general invalid traffic and sophisticated invalid traffic totals separately to prevent this data from being reverse engineered to optimise invalid traffic. Approximately 61% of total invalid traffic is estimated to be general invalid traffic.

Comprehensive unit test procedures are utilised to ensure the accuracy of reported data in the AdWords and AdSense frontends. These are the primary mechanisms utilised to ensure that data from backend databases are conveyed accurately in user-facing reports. In addition, user feedback is carefully monitored to discover and correct any errors which may make it through to a release. Numerous automated systems are in place to ensure the proper operation of all machines and software reporting data to AdWords users. The content of the reporting, however, is primarily verified through the aforementioned unit tests and user feedback.

Electronic records relating to click activity are retained indefinitely. However, two data fields, IP and cookie IDs, are anonymised after a specified time period (9 months for IP addresses and 18 months for cookie IDs).


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