Web annotation

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A web annotation is an online annotation associated with a web resource, typically a web page. With a Web annotation system, a user can add, modify or remove information from a Web resource without modifying the resource itself. The annotations can be thought of as a layer on top of the existing resource, and this annotation layer is usually visible to other users who share the same annotation system. In such cases, the web annotation tool is a type of social software tool. For Web-based text annotation systems, see Text annotation.

Web annotation can be used for the following purposes:

  • to rate a Web resource, such as by its usefulness, user-friendliness, suitability for viewing by minors.
  • to improve or adapt its contents by adding/removing material, something like a wiki.
  • as a collaborative tool, e.g. to discuss the contents of a certain resource.
  • as a medium of artistic or social criticism, by allowing Web users to reinterpret, enrich or protest against institution or ideas that appear on the Web.
  • to quantify transient relationships between information fragments.

Comparison of web annotation systems[edit]

Many of these systems require software to be installed to enable some or all of the features below. This fact is only noted in footnotes if the software that is required is additional software provided by a third party.


Annotation system Private notes Private group notes Public notes Notification Highlighting Formatted text Notes
A.nnotate Yes Yes No Yes[1] Yes No Can annotate PDF, ODF, .doc, .docx, images, as well as web pages (but only a limited number in the free version)
Annotary Yes Yes Yes Yes Yes No Includes social features, following, and a social feed of notes. Unlimited and free bookmarking, annotating, and collaboration. Private use allowed.
Chatterati No No Yes No No Yes Currently available as a Google Chrome extension. Allows its users to have a discussion, and vote on each other's comments.
Crocodoc Yes Yes No Yes Yes Yes HTML-based viewer, and offers support for mobile devices such as iPads and iPhones. Can highlight and annotate PDF, .doc, .xls, as well as web pages. Annotations are offered free of charge through a Crocodoc Personal account, and the viewer also allows for real-time collaboration with other users.
Delicious Yes No Yes No No No 1000 character limit per page per user
Diigo Yes Yes Yes Yes Yes No Public annotations are only allowed for established users. Group tag dictionary feature to encourage tagging consistently within a group.
Firefox (built-in) Yes No No No No No "Description" and "tags" fields of bookmarks provide this
Genius No No Yes Yes Yes Yes Genius (formerly Rap Genius) is an online knowledge base. The site allows users to provide annotations and interpretation of song lyrics, news stories, primary source documents, poetry, and other forms of text. Launching in 2009 with a specific focus on rap music, the site expanded in 2014 to cover other forms of media and released a platform for embedding annotations into other websites.
Hypothes.is Yes No Yes No Yes Yes In February 2015, different features are announced,[2] such as private group annotation, semantic tagging, moderation, etc.
Keeppy Yes Yes No Yes Yes No Allows annotate web site and stores the quote on the cloud server.
Org-mode (with extensions) Yes No No[3] Yes[4] No Yes Emacs-based; requires technical knowledge to set up; not as user-friendly as some other solutions; non-Latin characters allowed in notes but not in tags
rbutr No No Yes Yes No Yes More of a semantic linkage plugin than an annotation service, but it allows public comments and tags to be associated with rebuttal links. Rebutted pages display alerts which link to the rebutting pages with the comment that connects them.
Reddit Yes Yes Yes Yes No Yes Not primarily a web annotation site - public reddits (sections of the site) are mainly intended for new and/or interesting links, but private reddits can be used for anything. Voting up and down for links; links ranked by #votes and age; thumbnails for images and videos in list of links
Reframe It Yes Yes Yes Yes Yes No Compatible with Firefox, IE, Safari & Chrome. Websites can integrate a version of the tool directly into their sites. Allows replies for threaded discussions. Social network integration for sharing & signing in.
Scrible Yes Yes No No Yes Yes Caches a copy of the entire page to personal library along with annotations.
ShiftSpace Yes No Yes Yes Yes Yes Development has stopped.
Snowbound Software Yes Yes Yes No Yes Yes Annotations are XML-based. Available in HTML5 Viewer for Java and .NET as well as in our Viewing and Conversion SDK for Java, .NET, and Windows. Annotate any format supported including PDF, TIFF, Word, AFP, Excel, JPEG, TXT, HTML, and many more.
Stickis Yes Yes Yes Yes N/A[5] Yes Blogs subscribed via Stickis will appear as annotations when they link to the current page. Any web content, including YouTube videos, can be inserted into a note.
WebNotes Yes Yes No Yes Yes No Can also annotate PDF documents (but not in the free version). Highlighted PDFs and web pages can be shared with others, who do not need to install anything to view them.
Axiom[6] Yes Yes No Yes Yes No Axiom provides a better workflow to manage digital documents. It is a cloud-based collaboration platform that allows users to organize and annotate (mark-up) documents, web-pages and even videos. These digital assets and annotations can be shared to facilitate real-time collaboration. It empowers users to arrange their documents intuitively and it uses bookshelves to organize the documents, as opposed to the traditional file-folder system. Users can annotate using the pen, highlighter or sticky notes. These annotations can be labelled such that the tags can be used to cross-reference across all types of documents (including videos), which allows the user to manage their knowledge effectively. Axiom is also a social platform, and permits sharing of annotations and documents with others, making it easier to collect feedback on documents, web-pages or videos.
Marky Yes No No No Yes Yes Marky is a Web-based multi-purpose document annotation application (Social Admin-annotators application). You only need a server with php technology and one database to annotate documents with a browser. The annotation component handles both plain text and HTML documents. Web technologies, such as HTML5, CSS3, Ajax and JQuery, to offer an intuitive What-You-See-Is-What-You-Get editor. Admnins can enter documents to be annotated by annotators and get annotations for relevant terms.Marky also offers the possibility of obtaining substantial data about the annotations, as the annotation agreement between users, rounds, F-score and more. this is a tool that allows annotate multiple annotation classes, each with a different color. Developed in 2013. License GPL.

Technical details[edit]

Annotation system Cloud-based Technology Open source Bulk export
Firefox (built-in) No Bookmarks Yes Yes
A.nnotate Yes Snapshots No Yes[7]
Annotary Yes Toolbar No No
Chatterati Yes Chrome extension No No
Crocodoc Yes Snapshots No Yes
Delicious Yes Bookmarklet No Yes
Diigo Yes Toolbar No Yes[8]
Genius Yes Chrome Extension, Bookmarklet, iOS app, Web Proxy, Website Integration No No
Hypothes.is Yes Bookmarks, based on Annotator.js Yes No
Keeppy Yes Toolbar No Yes[9]
Org-mode (with extensions) No[10] Text editor Yes Yes
rbutr No Toolbar No No
Reddit Yes Toolbar Yes Yes
Reframe It Yes Toolbar, Bookmarklet, Website Integration No No
ShiftSpace No Greasemonkey Yes Yes
Snowbound Software No Viewer and Toolkit No Yes
Stickis Yes Toolbar No ?
WebNotes Yes Snapshots No ?
Axiom[11] Yes Online web-based HTML-5 No No
Marky Yes Online web-based HTML-5 Yes No

Former web annotation systems[edit]

  • The earliest web annotation system was probably CritLink, developed in 1997-98 by Ka-Ping Yee of the University of California.[12] CritLink worked as an HTML "mediator", hence not requiring additional software or browser extensions but having limited support for modern JavaScript-driven websites.
  • Annotea - a W3C project that tried to establish a standard for web annotation.
  • ThirdVoice - a system launched in 1999 that shut down due to lack of success in April 2001.[13]
  • Fleck* - launched in 2005 with much publicity as a stick-it notes application for the web. A patent, funding and marketing didn't stop it from failing. Discontinued in 2010.[14]
  • Google Sidewiki was part of Google Toolbar, and allowed users to write comments alongside any web page. It was discontinued in December 2011.
  • Dispute Finder was built by Rob Ennals while working for Intel. It attempted to automatically identify disputed claims on websites, highlight them, and link to comments and pages which corrected the dispute.
  • SharedCopy was an AJAX based web annotation tool that allowed users to mark-up, highlight, draw, annotate, cache, sticky-note and finally share any website.

See also[edit]


  1. ^ See A.nnotate notifications
  2. ^ Hypothes.is roadmap
  3. ^ Yes via the "publish to HTML" feature, but no notifications or discovery of public annotations written by others
  4. ^ With fireforg, which requires Firefox
  5. ^ Instead of highlighting a web page, you drag selected content from the webpage into the note.
  6. ^ http://www.axiomnetworks.ca/
  7. ^ via API
  8. ^ [1]
  9. ^ [2]
  10. ^ However, because .org files are plain text files, they can be backed up to the cloud at any time, using standard backup techniques/software. Emacs (in which org-mode runs) also supports saving to remote servers.
  11. ^ http://www.axiomnetworks.ca/
  12. ^ Yee, Ka-Ping (2002). "CritLink: Advanced Hyperlinks Enable Public Annotation on the Web". CiteSeerX: 
  13. ^ Third Voice Trails Off, Wired News, April 4, 2001
  14. ^ Farewell Fleck.com, "The Next Web", May 10, 2010

Further reading[edit]

External links[edit]