Reduce latency with Prebid server and Lazy loading

Let’s begin with prebid

The majority of header bidding integrations are done in prebid.js because it is free and open source. With prebid.js client side integration, one request is done from the user’s browser for each SSP involved and sometimes for each ad slot. This is causing several DNS lookups and HTTP connections and requests, that eventually monopolize network resources and delay page loading. Web performance studies have proven that user engagement decrease by 10% for each second of additional latency.


When using prebid server, only one request is done (to the prebid server) whatever the number of SSPs involved in the auction. This limits resources used to fill ad slots, optimizes page load time and increases user engagement. Prebid server is the best solution in terms of latency and user experience. However, not all SSPs offer prebid server integration yet, but this could rapidly change.

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Lazy Loading of ads

With lazy loading, an ad not above the fold is loaded when the user scrolls down, just before the ad appears on screen. This reduces the number of ad requests, and thus the page load time, when the page is initially loading. This may result in inventory size reduction while improving viewability rate: the lower the original viewability rate, the higher the inventory loss.

What’s next

In both cases it can improve latency issues while using header bidding. With prebid server all header bidding requests take place in the server at the same time and with lazy loading the number of requests is reduced due to loading the ads one at a time by scrolling down. To avoid inventory losses there can be another solution: Smart loading. Find out more in the next post.