Life of an Ad Request

Last Updated: 2022-02-01


Both are ad mediation techniques: requests are sent to several demand partners simultaneously.


  • Header Bidding or Pre-bidding: NOT created by Google. A publisher runs an auction on its webpage/app before sending an ad request to Google Ad Manager. Client side (publishers place HTML or JavaScript code in the header of their site to run a real time pre-assessment).
  • Open Bidding: owned by Google, as an reaction to Header Bidding. Server-side (the auction will be happening inside GAM), unified auction; 3rd party ad exchanges compete with Google's AdX

Header Bidding

A programmatic advertising technique in which publishers bid on multiple advertising exchanges in real time. Publishers make 3rd party exchange compete with Google Ad Manager

  • AdX - GAM - header bidding
  • Exchange - header bidding

Open Bidding

Google’s “auction of auctions”

  • AdX - OB - GAM
  • AdX - OB - AdMob
  • AdX - Exchange - GAM
  • AdX - Exchange - AdMob