What is Ad Network and Why Do Publishers Need One (or More)? In a simple inventory selling process, think of an ad network as a mediator responsible for introducing the right impression to the right buyer. It partners up with publishers (supply-side) and advertisers (demand-side) to help them reach their ad campaign goals. Now, as the inventory exchange cycle gets complicated, the role of ad networks starts varying. For publishers, ad networks sometimes directly sell inventory, and at other times, buy inventory from SSPs or ad exchanges and sell it for a greater profit. Most publishers are known to specialize in one particular type of ad format. Hence, publishers looking to monetize via one particular format should consider ad networks. For instance, there are CPM ad networks like Criteo known to offer the best CPM rate and then there are video ad networks like Unruly serving publishers with the best video content. Additionally, ad networks are ...