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Ad Serving 101: How It Works for OOH


If you search for the definition of “ad server”, you’ll get a lot of different answers. That’s because ad servers have been around for years in the online space, and serve different functions depending on who is using them. Online advertisers (buyers) use ad servers to manage their creative and track performance of their ads across the internet. Publishers (sellers) use ad servers to manage campaigns they’ve sold to run on their sites or mobile apps. 

In order to understand how ad serving works in digital out-of-home, you need to know the difference between a CMS and an ad server.

A traditional CMS (content management system) is a scheduling engine

An ad server is a decision-making engine.

What’s the difference? 

Today, you probably use a CMS to manage the ads and content that appears on your screens. Most CMSs are designed to deliver a predetermined schedule or loop. When you sell a campaign, you enter it into your CMS (e.g. “1 spot in your loop for 4 weeks”), select the screens you want to run the ads on, and your CMS pushes a schedule to your screens in the field. Your devices store the schedule, and if everything goes according to plan, your screens loop over the schedule until they get something new from your CMS. 


Traditional CMS - DOOH


An ad server operates differently. Rather than pushing a predetermined schedule to your screens, your screens “pull” the most relevant ad for each spot in real time by making “requests” to the ad server. You give the ad server rules for each campaign you sell (e.g. “deliver 1MM impressions, in the following zip codes, over the next 4 weeks). When a screen needs an ad to play, it will ask the ad server in real-time for an ad. The ad server will look at all the campaigns it needs to deliver and pick the best one based on the rules you’ve defined.  




Both a CMS and ad server are imperative to operating a successful digital out-of-home network — but leave the CMS to manage your content. By limiting your network to only sell a spot in a loop, you're leaving revenue on the table. Optimize your inventory, and take the headache out of scheduling with an ad server.

To learn more about Vistar’s ad serving solutions or for a free demo, contact us.

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