MetaXchain also known as a MetaX is a blockchain technology company headquartered in Santa Monica, California focusing on the development and adoption of open platforms for the digital advertising industry. The company is best known for developing the adChain protocol.  
MetaXchain's founded the adChain protocol with ConsenSys. The first product developed by MetaXchain as part of the adChain protocol is the adChain Registry a Token Curated Registry of domain names. The registry is designed to be used as a base to provide the digital advertising industry with a decentralized repository of trustworthy websites accredited by adToken holders.  Advertisers will be able to utilize the adChain Registry as a public utility as it will help them protect their ad spend dollars against the problem of ad fraud which in 2017 cost advertisers $16.4 billion dollars. 
The adChain Registry is currently in Beta on the Rinkeby Testnet. 
Ads.txt Plus, is a decentralized application (DApp) currently deployed on the Ethereum testnet that leverages the blockchain to supplement ads.txt. The DApp uses a simple user interface to enable publishers to add their sellers to the blockchain and for buyers to search for their respective publishers.  Ads.txt offers a solution for publishers and content owners to list the authorized sellers of their inventory in a .txt file served from within the root path of their domain’s web server.