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Zotero works through extensions and plugins for Firefox, Chrome, Safari and Edge, which you can download from the Zotero website. There is also a standalone version for Macs 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.
Plug-ins, available for Microsoft Word, LibreOffice, and Google Docs, create dynamic bibliographies: insert a new in-text citation in your manuscript, and the bibliography will be automatically updated to include the cited item.
PowerNotes is a productivity tool, used as an extension in Chrome or Firefox, that lets you grab quotes from texts you are reading online, grab citation info, add notes, and turn these notes into an outline and then a paper.