Unfortunately, it looks like the crawler’s coverage is still relatively poor. I just spot-checked five of my own articles (all of which are self-archived on my academic website, among other places), and it could find an open-access PDF for only one of them. Google Scholar, meanwhile, found multiple open-access PDFs for all of them.
I think https://oadoi.org/ is a way to use this without the extension.
Unfortunately, it looks like the crawler’s coverage is still relatively poor. I just spot-checked five of my own articles (all of which are self-archived on my academic website, among other places), and it could find an open-access PDF for only one of them. Google Scholar, meanwhile, found multiple open-access PDFs for all of them.