Currently there are two versions of Zotero offered for download: Zotero 1.0 and Zotero 2.0 Beta. Zotero 2.0 Beta offers many new and exciting features, but ongoing development may cause minor problems for some users as detailed below.

• Syncing and backup of Zotero libraries
• Automatic detection of PDF metadata
• Rich-text notes
• Create and join public and private groups on any topic.
• Access in real time new research materials from your groups on the web or in the Zotero interface.
• Easily move materials from a group stream into your personal library.
• Automatic detection and support for proxy servers
• Trash can with restore item functionality
• Support for Endnote® export styles

• 1.0 Word Processor Plugins
• 2.0 Beta Word Processor Plugins

Zotero 2.0 Beta has already been tested by thousands of users over the last months, and we are confident that it is ready for widespread use. We have also added additional automated functionality to Zotero 2.0 Beta to protect data against loss. However, we are still actively adding features to Zotero's synchronization functionality, and there is always a small risk of losing your data. If this message scares you even a tiny bit, please continue to use Zotero 1.0.x for the time being. When using Zotero 2.0 Beta, we strongly advise you to back up your data regularly.

If you are already using Zotero 1.0, there are several additional considerations related to upgrading, discussed here.