Shelfpass — free and library copies of papers

Hit a paywall? Shelfpass checks whether the paper you're looking at is legally available for free, and tells you where. It reads the page for a DOI, arXiv ID or PMC ID, then asks OpenAlex and Crossref two questions: is there an open access copy, and has this paper been retracted. You get one verdict and a link. Warns you before you cite something retracted. Retractions, withdrawals and expressions of concern are flagged in red, drawn from Crossref's public record. Most access tools skip this entirely, and a retracted paper reads exactly like a sound one. Finds the free copy the publisher doesn't mention. Author manuscripts in repositories, preprints on arXiv, and full text in PubMed Central — all legal, all frequently available while the publisher's own page asks for £35. Your library, on your terms. If your institution has a proxy, add the pattern once and Shelfpass offers that route when nothing free exists. EZproxy, OpenAthens and hostname-style proxies are supported. That pattern lives on your computer, not on our server, because there isn't one. Nothing runs until you ask. Shelfpass installs with no permission warnings and no page access. It reads a page when you click the button, or on individual sites you've allowed. You can revoke any of them at any time. No account, no identifier, no analytics. There's no sign-up, no install ID, and no usage events. The only thing that leaves your browser is the identifier of a paper you asked about, going to public scholarly APIs. The whole extension is under 100 KB. Built for researchers, students, reviewers and librarians who want one honest answer about a paper, not a dashboard. Data from OpenAlex, Unpaywall, Crossref and Europe PMC, each under their own terms. Not affiliated with any of them.