When you load a new webpage, the Unpaywall extension scans the text of that page looking for a DOI (a short unique identifier key used by scholarly articles—it’s like a URL for academic papers). If it finds one, we send that DOI over the internet to our API in order to retrieve our best Open Access location for the article.

This is the only time Unpaywall connects to a remote server. The information sent is:

• The DOI, which is needed to look up article information.
• The IP address of your computer, which is needed for all internet requests (This part is not unique to Unpaywall—Firefox sends your IP address to every server it connects to and every webpage you visit. You can hide your IP address by using a VPN).

Unpaywall does not send your name, email address, or any other content of the pages you browse to our server (except the DOI). Unpaywall does not know or have access to your name or email address.

Records of individual requests are not shared with third parties. They are stored as part of our server logs, which we use for debugging and load analysis. Our server logging system vendor is Papertrail. Aggregated data, stripped of all personal information, may be shared with third parties or published as part of statistical research on Open Access trends and usage. For example, we might make a blog post saying “Unpaywall delivers Open Access articles in 50% of user requests.”

Unpaywall uses local storage to save user settings.

Unpaywall's source code is hosted on github.com.