Open Access Helper for iOS / iPadOS
Open Access Helper is an iOS app, designed to be used as an Action Extension. It will identify Digital Object Identifiers (DOI) within the page's source code (meta-tags) and then use unpaywall.org API to find a legal Open Access copy for the document you are viewing.
Additionally it will check core.ac.uk for a legal Open Access copy and, if you so chose, offer to request via Open Access Button (https://openaccessbutton.org) or via a CORE Recommender Recommendation and more.
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About the code
This app is a hobby project, I am sure there is plenty in the code that isn't perfect or best practice. If you see something, feel free to open an issue.
I guess there is Copyright and I guess it is mine ;)