Zotero started as a free Firefox extension. You can download extensions and plugins for Firefox, Chrome, Safari and Edge from the Zotero website. There is now also a standalone version that can be used with other browsers, and a web version that can be used on shared computers, like ones in the library or campus computer labs. If you are using Zotero on a public or shared computer, restart when you are done to avoid anyone making changes to your collections.
EndNote Web is another free online tool. Very helpful documentation is available. Can include attached documents. Can export to other citation managers. Can export directly from VSC Online Catalog to EndNoteWeb. Can export directly from EBSCO databases, for others: generate an .ris file.
Mendeley is another free tool, which is more than a citation manager. You can search within it, and use it to store documents. You can sync your desktop files with Mendeley Web.
To use, you make an account, download “Mendeley desktop,” and install “Mendeley Web Importer” (works like a bookmark; when you click on it, it grabs citation info from webpage). See How to install “web importer.”
To export from subscription databases, choose "Reference Manager." Exports as an .ris file. If you have Mendeley installed, click on the RIS file and Mendeley will open up.
For tablets and mobile devices: Mendeley for iOS (You can access your citations and links and add PDFs to your account). No Android app yet.