Counting Methodology

Basis DSP counts impressions and clicks following the IAB Impression Measurement Guidelines and Click Measurement Guidelines, with some slight adjustments to account for RTB-specific concerns that were not considered in the most recent version of the guidelines.


Before Basis DSP counts an impression, it must be preceded by:

  • a bid request from an exchange (an auction), and
  • a valid bid

Impressions are counted in one of a few ways depending on the exchange and circumstances:

  • Impression tracking pixel in markup: An impression tracking pixel is placed (as an image call) in the creative markup used in our bid response. An impression is counted when a client-side browser fetches this URL.

  • Impression tracking URL: An impression tracking URL is supplied in our bid response, in a separate field from the creative markup. An impression is counted when this URL is called. Depending on the circumstances, this URL is either a) appended to the markup by the exchange and fired client-side by the browser when it fetches the ad markup, b) triggered client-side by the exchange when the ad is rendered, or c) triggered server-side by the exchange when the exchange's client-side pixel fires.

  • Video VAST impression event: Video impressions are always counted on the basis of the player triggering the VAST Impression event. 

Generally, impressions are counted when the client fetches the assets. In some cases, this is less than ideal. For example, mobile interstitial impressions are pre-cached by the device up to several minutes before the ad is shown to improve user experience. In the event that the app is abandoned, the impression may never actually be rendered at all, in which case counting upon fetching of markup would result in impressions being counted that had no chance to be seen.

Wherever possible (that is, when exchanges support this method), Basis employs the impression tracking URL method so that an impression can be counted when an ad is actually rendered. Third-party ad servers may count substantially higher for certain ad formats such as interstitials if the ad server uses a count-on-fetch method. When server-side counting is used, Basis's RTB Platform Operations team periodically checks counting accuracy against a tracking pixel included in creative markup.

Exchanges provide the clearing price of the auction in the impression tracking pixel/URL. The clearing price must be present to be considered a valid impression. Only one impression is counted per auction.


To be counted by Basis DSP, a click must be preceded by a valid impression as defined above. Basis DSP only counts one click per impression. Clicks must occur within 24 hours of the impression to be counted.


Impressions and clicks are subject to filtration for known non-human activity. Auctions are excluded from consideration (and as a result, impressions do not occur) if:

  • The bid request contains a user agent that is either a) on the IAB list of user agent patterns of known spiders and bots, or b) not on the IAB list of known valid user agent patterns, or

  • The bid request contains an IP address that is known to be in a data centre.

Clicks are likewise discarded if they meet the same criteria, except that the user agent and IP address are directly observed by Basis's servers when the click occurs.

This document considers only filtration required for consistency with the IAB Measurement Guidelines. We also employ additional bid request filtration for sophisticated fraud prevention.

Automated Creative Scanning

All ads used on Basis DSP may be subject to automated creative scanning to detect malicious activity. These scans simulate impressions and clicks on an ad as it might be experienced by a user. This scanning occurs outside of the process of bidding on auctions, so impressions and clicks occurring as a result of Basis's scanning are not counted in the DSP. These scans may occur multiple times per day from a variety of different geographical locations and browser/device types. Exchanges or publishers may also subject creatives to additional scanning. When exchanges do such scanning, a valid clearing price is not provided in our impression tracking pixel/URL, and, as a result, we do not count an impression.

Third-party ad servers may record impressions and clicks that result from automated scans depending on the sophistication of their filtration.

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