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 (like 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.

Annotations can be considered an additional layer with respect to comments. Comments are published by the same publisher who hosts the original document. Annotations are added on top of that, but may eventually become comments which, in turn, may be integrated in a further version of the document itself.[1]

Standardisation efforts[edit]

Web annotations were first standardised on February 23, 2017 with the release of three official Recommendations by the W3C Web Annotation Working Group[2]:

  • Web Annotation Data Model
  • Web Annotation Vocabulary
  • Web Annotation Protocol

The W3C also had a previous web annotation standardisation effort, Annotea (see below), which was conceived of as part of the semantic web.

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 Archives Viewing annotations API License Notes
A.nnotate Yes Yes No Yes[3] Yes No Yes Yes Proprietary Can annotate PDF, ODF, .doc, .docx, images, as well as web pages (but only a limited number in the free version)
Diigo Yes Yes Yes Yes Yes No Yes Yes Proprietary Public annotations are only allowed for established[definition needed] users. Group tag dictionary feature to encourage tagging consistently within a group.
Firefox (built-in) Yes No No No No No No Bookmark properties Yes MPL "Description" and "tags" fields of bookmarks provide this
Genius No Yes Yes Yes Yes Yes Chrome, via genius.it Yes Proprietary Genius has a Chrome Extension, an iPhone App, and a subdomain (genius.it/) which you can prepend to any domain to annotate. This is in addition to their website, genius.com, where users can annotate lyrics, literature, news, and other categories.
Hypothes.is Yes Yes Yes Yes Yes Yes Chrome, via.hypothes.is Yes MIT, BSD In February 2015, different features were announced,[4] such as private group annotation, semantic tagging, moderation, etc.
Org-mode (with extensions) Yes No No[5] No[6] No Yes 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
parley.today No No Yes Yes No No Yes Via parley.today/ or Disqus No Proprietary Broswer-based. The subdomain (parley.today/) can be prepended to any domain to annotate/comment.

Discontinued web annotation systems[edit]

System Notes Date Discontinued
Mosaic Browser An early version of the Mosaic browser was tested with collaborative annotation feature in 1993[7] but never passed the test state. Never passed the test state
CritLink Perhaps the earliest web annotation system. Developed in 1997–98 by Ka-Ping Yee of the University of California.[8] 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.[9] April 2001
Delicious Founded in 2003 and provided cloud bookmarks with optional descriptions (a form of annotation) of up to 1000 characters. It was rumoured that it would be shut down in 2010, but it was only actually finally shut down in 2017 when it was acquired by Pinboard, a competitor. 2017
Wikalong A Firefox plugin created in 2004 that provided a publicly editable mediawiki page in the margin of any webpage. (It was later accessible in other browsers via a bookmarklet.) Common uses were note-taking and discussion about the website. On Google, the Wikalong margin provided a variety of useful tips and shortcuts for searching. The project was discontinued in 2009 when the storage wiki went offline. It had been suffering from link spam abuse.[10][11] 2009
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.[12] 2010
Stickis Launched in 2006, focused primarily on tight-knit communities, and allowed them to create a blog of annotations.
stet Stet was the Gplv3 comment system.[13]
Crocodoc Launched in 2007, dabbled in web page annotation as part of its broader mission. It was originally developed in Adobe Flash. It was acquired by Box.com in 2013[14] and the web annotation side of it was shut down two years later.[15] 2009
ShiftSpace Started in 2008. A tool for artistic and political subversion and reimagining of websites. Development stopped in 2011. 2011
Blerp Launched in 2009. A multimedia, extensible tool for annotating web pages with widgets viewable by any other Blerp user.
Google Sidewiki Launched in 2009. A part of Google Toolbar that allowed users to write comments alongside any web page. It was discontinued in December 2011. December 2011
Dispute Finder 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 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. ^ Doug Schepers. "Web Annotation Architecture". W3C. Retrieved 29 July 2016.
  2. ^ Whaley, Dan (February 24, 2017). "Annotation Is Now a Web Standard". Hypothes.is.
  3. ^ See A.nnotate notifications
  4. ^ "Trello". hypothes.is.
  5. ^ Technically, public annotations are possible via the "publish to HTML" feature of org mode -- but no method for notifications or discovery of public annotations written by others is currently known.
  6. ^ But local annotations can be exposed to a firefox browser using Fireforg.
  7. ^ Andreessen, Marc (1993-05-31). "group annotation server guinea pigs?". webhistory.org. Retrieved 2017-11-08.
  8. ^ Yee, Ka-Ping (2002). "CritLink: Advanced Hyperlinks Enable Public Annotation on the Web". CiteSeerX: Missing or empty |url= (help)
  9. ^ Third Voice Trails Off, Wired News, April 4, 2001
  10. ^ Wikalong Firefox Addon, Oct 1, 2006
  11. ^ "SEO – SEO-Optimierung". www.wikalong.org.
  12. ^ Farewell Fleck.com, "The Next Web", May 10, 2010
  13. ^ "Comment system". Free Software Foundation. 11 May 2011. Retrieved 28 July 2016.
  14. ^ "Box acquires Crocodoc to turn all those docs you upload into HTML5 masterpieces". VentureBeat. 9 May 2013. Retrieved 12 June 2016.
  15. ^ "Box is Shutting Down Crocodoc Personal and Webnotes on November 1". VentureBeat. 5 August 2015. Retrieved 12 June 2016.

Further reading[edit]

External links[edit]

  1. Web Annotation Data Model
  2. Web Annotation Vocabulary
  3. Web Annotation Protocol