Diigo
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Diigo is a social bookmarking website that allows signed-up users to bookmark and tag Web pages. Additionally, it allows users to highlight any part of a webpage and attach sticky notes to specific highlights or to a whole page. These annotations can be kept private, shared with a group within Diigo, or be forwarded to someone else via a special link. The name "Diigo" is an acronym from "Digest of Internet Information, Groups and Other stuff".
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Diigo ("Digest of Internet Information, Groups and Other stuff") allows users to bookmark web pages, annotate, highlight and share them. You can also discover resources other people have bookmarked.
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Encyclopedic overview
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Diigo is a social bookmarking website that allows signed-up users to bookmark and tag Web pages. Additionally, it allows users to highlight any part of a webpage and attach sticky notes to specific highlights or to a whole page. These annotations can be kept private, shared with a group within Diigo, or be forwarded to someone else via a special link. The name "Diigo" is an acronym from "Digest of Internet Information, Groups and Other stuff".
Premium account holders can perform full-text searches of cached copies of bookmarks. A full-text search also searches page URLs, tags and annotations. This means that premium account holders can choose to omit tags that already appear in the text of a page to be bookmarked (although text inside images cannot be searched).
Excerpted from Wikipedia’s “Diigo” article, available under the CC BY-SA 4.0 licence.