• Impression is considered a viewable impression when it has appeared within a user’s browser and had the opportunity to be seen. 
  • The Interactive Advertising Bureau (IAB) defines a viewable impression as an ad that meets the following criteria:
    • For ads, 50% of the ad’s pixels are visible in the browser window for a continuous 1 second. 
    • For larger ads (those greater than 242,000 pixels), 30% of the ad’s pixels are visible in the browser window.
    • For in-stream video ads, 50% of the ad’s pixels must be visible in the browser window for a continuous 2 seconds.