AdEx originated in 2017 as a decentralized ad exchange for digital advertising, and subsequently evolved into a full protocol for decentralized digital advertising. The AdEx protocol facilitates trading of advertising space/time, as well as the subsequent verification and proof that it actually occurred. Essentially, it covers all interactions between publishers, advertisers and end users. The protocol combines traditional peer-to-peer technology, cryptography and blockchain. The rationale for creating the AdEx protocol was to create an open-source, transparent and fraud-proof replacement to the entire existing stack. By introducing real-time tracking and reporting directly accessible to each advertiser and publisher, and dropping the need for most intermediaries, we dramatically reduce the ability for any side to report wrong data to others for their own financial gain.