Mendeley is a citation manager run by Elsevier. It is available as a free desktop download (Mendeley Reference Manager) for Mac, Windows, and Linux with access to a web-based version of your library.
Free v. pay:
Mendeley software and web library access is currently free. Additional storage can be purchased.
You can access your Mendeley library on the web via the Mendeley site.
Mendeley does allow for storage of files within your library. Mendeley's free online storage is limited to 2 GB and additional storage can be purchased via the Premium Packages page.
Integration with other products:
Mendeley can export resources in a format readable by most other bibliographic software including EndNote/EndNote Basic.
Mendeley can be collaborative. You can create groups and share library folders with them. You can even make them public if you like.
The easiest way to get records into Mendeley is by downloading the PDF of the article and then dragging and dropping the PDF into your library within Mendeley Reference Manager or your online Mendeley library. Mendeley also with the .ris file type that is common among bibliographic software applications. You can also manually add items to your library as well as create an item out of any web page you might be visiting using the Mendeley Web Importer plug-in.
Mendeley comes preloaded with all major styles, and thousands of additional journal-specific styles are freely available.
Prior to September 1, 2022, the desktop application for Mendeley was called Mendeley Desktop. This is a separate application from the new Mendeley Reference Manager. If you previously installed Mendeley Desktop and are happy with it, it will still work for the time being, however the installation software for it is no longer available and the default application is now Mendeley Reference Manager.
Instructions are available if you would like to migrate from Mendeley Desktop to Mendeley Reference Manager.