September 9, 2021
An ad impression is an ad which is served to a user’s browser. Ads can be requested by the user’s browser (referred to as pulled ads) or they can be pushed, such as e-mailed ads. An ad impression is a measurement of responses from an ad delivery system to an ad request from the user’s browser, which is filtered from robotic activity and is recorded at a point as late as possible in the process of delivery of the creative material to the user’s browser—therefore closest to the actual opportunity to see by the user. Two methods are used to deliver ad content to the user.
**Server-initiated – Server-initiated ad counting uses the publisher’s web content server for making requests, formatting and re-directing content.
**Client-initiated – Client-initiated ad counting relies on the user’s browser to perform these activities. For organizations that use a server-initiated ad counting method, counting should occur subsequent to the ad response at either the publisher’s ad server or the Web content server. For organizations using a client-initiated ad counting method, counting should occur at the publisher’s ad server or third-party ad server, subsequent to the ad request, or later, in the process.