Real-time bidding

Real-time bidding (RTB) is a means by which advertising inventory is bought and sold on a per-impression basis, via instantaneous programmatic auction, similar to financial markets. With real-time bidding, online advertising buyers bid on an impression and, if the bid is won, the buyer's ad is instantly displayed on the publisher's site.^[2] Real-time bidding lets advertisers manage and optimize ads from multiple Ad networks, allowing them to create and launch advertising campaigns, prioritize networks, and allocate percentages of unsold inventory, known as backfill.^[3]

Real-time bidding is distinguishable from static auctions by how it is a per-impression way of bidding, whereas static auctions are groups of up to several thousand impressions.^[4] RTB is promoted as being more effective than static auctions for both advertisers and publishers in terms of advertising inventory sold, though the results vary by execution and local conditions. RTB replaced the traditional model.

Research suggests that RTB digital advertising spend will reach $23.5 billion in the United States in 2018 compared to $6.3 billion spent in 2014.^[5]