Zotero

Zotero is a free, easy-to-use tool to help you collect, organize, annotate, cite, and share research.

Zotero automatically senses research as you browse the web. Need an article from JSTOR or a preprint from arXiv.org? A news story from the New York Times or a book from a library? Zotero has you covered, everywhere.
Zotero helps you organize your research any way you want. You can sort items into collections and tag them with keywords. Or create saved searches that automatically fill with relevant materials as you work.
Zotero instantly creates references and bibliographies for any text editor, and directly inside Word, LibreOffice, and Google Docs. With support for over 10,000 citation styles, you can format your work to match any style guide or publication.
Zotero can optionally synchronize your data across devices, keeping your files, notes, and bibliographic records seamlessly up to date. If you decide to sync, you can also always access your research from any web browser.
Zotero lets you co-write a paper with a colleague, distribute course materials to students, or build a collaborative bibliography. You can share a Zotero library with as many people you like, at no cost.
Zotero is open source and developed by an independent, nonprofit organization that has no financial interest in your private information. With Zotero, you always stay in control of your own data.