Zotero works with Firefox (3.0 and up) and Flock (2.0 and up) for Windows, Mac and Linux. Other browsers, like Internet Explorer and Google Chrome, currently lack the extension architecture to support many of Zotero's most useful features, such as the ability to sense and grab citations from web pages. In addition, even if support for extensions were improved, porting Zotero to other browsers would still require a complete rewrite of the software. For these reasons there are no immediate plans to support other browsers.

These technologies do not provide the functionality needed by Zotero, including but not limited to the following:

• full and persistent integration with the native browser UI
• access to the currently loaded document from site translators
• local file I/O with stream and character set support
• dragging/dropping text/files to/from the OS
• copying content to the clipboard
• opening a local socket for word processor integration
• observing and rewriting HTTP requests for 1.5's advanced proxy support
• observing HTTP responses for automatic RIS/CSL ingestion
• gzip support for fast syncing
• RDF support for import/export
• automatic locale support
• external process launching for PDF indexing
• an idle observer for running backup and sync operations
• flexible attachment opening
• revealing files in the filesystem

Google Gears, Opera Widgets and/or various HTML 5 API proposals might provide partial support for a few of these things, but nowhere near what would be needed to approximate current Zotero functionality.