Programmatic
Ad call
An ad call is the HTTP request an ad tag makes asking an ad server or partner to return an ad; it is often a synonym for ad request.
An ad call is what an ad tag actually does on the wire: a browser or app makes a network call to a URL with parameters describing the slot, page and device, and the server responds with an ad or a redirect to one. In practice many people use "ad call" and ad request interchangeably.
Where teams distinguish them, "ad request" is the publisher-side ask for an ad, and "ad calls" are all the individual calls that follow: to the publisher ad server, to an exchange, to an advertiser ad server that hosts the creative, and to verification or tracking pixels. A single visible ad can involve many ad calls, especially when redirects chain from one system to the next.
Every extra ad call adds latency and a possible failure point, and is a spot where discrepancies arise, because each system counts at a slightly different moment. Ad calls to unexpected domains in a creative can also indicate malvertising.
Think of it like this
An ad call is like each phone call in a chain of referrals: the receptionist calls the manager, who calls the warehouse, until someone sends the parcel.
An example
A video ad makes one call to the publisher ad server, one to an SSP, a redirect call to the advertiser's ad server for the VAST file, and three tracking calls: six ad calls for one ad.
Related terms
Ad request
An ad request is the signal a web page, app or video player sends to an ad server or ad platform asking for an ad to fill a specific slot.
Ad server
An ad server is the software that stores ads, decides which ad to show in each slot based on rules and priorities, delivers it, and counts impressions and clicks.
Latency
Latency is the time delay between a request and a response; in advertising, it is how long auctions, ad servers and creatives take to return and display an ad.
Discrepancy
A discrepancy is the difference between numbers reported by two systems for the same campaign, such as a publisher's and an advertiser's ad server counting different impressions or clicks.
Tracking pixel
A tracking pixel is a tiny piece of code, historically an invisible 1x1 image, that loads when a page or ad is viewed and reports that event to a server.