(Googler ADX is more in the middle of the two)
Yes, Google Ad Exchange is an SSP or a Supply Side Platform. Google AdX allows large publishers, who have monthly traffic of 5 million and more, to have more control over their ad monetization strategy and find better CPM, which results in a revenue boost, not minted to 30-50%.
As AdX serves the supply side of the network, ie. publishers, it is primarily known as an SSP. AdX is managed by Google Ads Manager which is also Google’s SSP or ad server. It enables publishers and digital media owners to sell ad spaces through an automated auction. According to Total Media “AdX outperforms the competition by connecting publishers into the world’s largest exchange of global inventory.”
It is a neutral, autonomous platform, that allows for programmatic ad buying, driven by real-time bidding (RTB) technology.