oaDOI is a recently-launched tool which works similarly to a DOI, by directing users to a perma-link for a given article. The key difference is that oaDOI is OA-friendly: it will direct end-users to OA versions of the article if one is available. [link]
The tool has two parts, a link-generating service similar to bit.ly and other link shorterners, and an API that can be used to implement this behavior in other environments.
Generate an oaDOI link
The link-generating service is simple to use. Just get the DOI link for an article and paste it into the textbox at https://oadoi.org/.
The system will process the request and provide you with an oaDOI link you can distribute to direct users to an OA version of the article, if possible:
As seen above, the results page also describes whether the system was able to find an OA version or not, and if so where and how open that version is. The system will also provide a link that contains API information.
API
The API is for more advanced users who wish to take advantage of the system’s ability to find OA articles in other contexts (e.g. in an OpenURL resolver).
The oaDOI API page provides a run-down of functionality and example code, as well as a few use cases of other code libraries and projects which are using the API.