In a few words: Exciting and congrats to the Unpaywall team!
From the Europe PMC Blog:
In Europe PMC, free full text is already available for 4.6 million out of 33 million records. As for the rest, an open access copy may exist in a different repository, or reside on the publisher’s website. However, users have no way of knowing that the article they are interested in may be available elsewhere. And that happens more often than you think. According to a recent study, nearly half of all scientific articles requested by Unpaywall users are already available from one of the open sources.We believe in the power of open science, but to unlock its true potential open content needs to be easily discovered. To help address this issue, Europe PMC has teamed up with Unpaywall to help users get open access to publications easily.You can now see the iconic green Unpaywall logo on the full text link on the Europe PMC website whenever a free version of the paper can be found using the Unpaywall service.