The most popular article on this blog is one of the very first ones I ever wrote – How Does Ad Serving Work. What I probably should have titled it though was How Does Ad Serving Work on the Web, because there are a few important differences when you’re talking about the mobile ecosystem.
Server Redirects vs. Client Redirects
For the most part, it comes down to the interaction between a client and a server – in desktop environments, the user’s browser, or the client in technical-speak, does most of the work fetching and redirecting information, which is ideal for lots of reasons. For one, redirecting the client gives each platform in the ecosystem the ability to drop or read a cookie, which helps with downstream conversion tracking, frequency measurement, and audience profiling. Secondly, it facilitates client-side tracking of key metrics like clicks and impressions for billing purposes. Client-side tracking is the preferred methodology for advertisers because it measures requests from a user instead of from a server, and is therefore a more accurate measure of what a user actually saw. This process requires more work from the browser, but that’s OK because high-speed connections and unlimited data usage is pretty much the norm these days for home and office connections.
In mobile environments though, connection speeds really matter. Many users are on slow enough connections that if the browser or app was responsible for fetching the ad the way it does on desktop connections, the user is likely to abandon the page before the ad finished loading. Because of that, you often see more of the work being done in the cloud for mobile ad serving, independent of the client. So instead of the browser calling a server, and then being redirected to another server, the browser tends to call a server, which then calls other servers, which can talk to each other through the ultra-fast fiber-optic landlines instead of the cellular network. (more…)