OpenRTB is an open source protocol and set of APIs used by the RTB industry to facilitate this real time bidding process between buyers and sellers. Open RTB or Open Real Time Bidding is an industry specification for the programmatic buying and selling of advertising. The current most deployed version is oRTB 2.5 defined by the IAB Spec. It provides a common language that both sides can use to communicate information such as price, ad size, and target audience. OpenRTB has become an industry standard and is supported by most major DSPs, SSPs, and exchanges.