Unpaywall is an open database of over 23 million research articles, instantly, for free!
All you need to do is install the Chrome extension or Firefox add-on then when you are searching online for a paper, if it’s on a website that asks you to pay for it, the extension gets to work looking for a free copy of it. This can be an invaluable tool for your research projects.
Take a look at this video to see how simple it is. I can now read about a circumbinary protoplanetary disk in a polar configuration to my heart’s content.
Is it legal?
Don’t worry, it’s 100% legal! Where some journals make the papers available to sell, the authors themselves often post their content on alternative sites or host their own repositories allowing their work to be benefitted by everyone. Unpaywall points you to legal, author-posted manuscripts that are hosted on university and government web servers. We are pointing to versions that have been posted with the full and explicit authorization of the publishers themselves.