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

The W3C has a Web Annotation Working Group which has issued 3 Recommendations:

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

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
DataTurks Yes Yes Yes No Yes Yes Yes Yes Yes Free for hobbyist + Custom for Enterprises Can annotate PDF, .doc, .docx, images. Free version will be open to public. Paid version keeps data private and more number annotators.

Example annotation: https://dataturks.com/projects/Dataturks/Demo%20Document%20Annotations

A.nnotate Yes Yes No Yes[2] 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)
Annotary Yes Yes Yes Yes Yes No Includes social features, following, and a social feed of notes. Unlimited and free bookmarking, annotating, and collaboration.
Axiom[3] Yes Yes No Yes Yes No Yes No Proprietary 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.
ChimeIn No No Yes Yes No No No A browser extension available for Chrome, Safari, Opera, Firefox and Internet Explorer. Works as a standalone app on iOS and Android. Full social integration and notifications in email and push messages.
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.
DocentEDU Yes Yes No Yes No No Chrome, Firefox No Proprietary Allows turning any website into an educational lesson.
Epiverse No No Yes No No No No Browser extension for Chrome and Firefox. Includes comments sourced from Reddit.
Firefox (built-in) Yes No No No No No No Bookmark properties Yes MPL "Description" and "tags" fields of bookmarks provide this
FactualNote Yes Yes Yes Yes Yes Yes Chrome, via factualnote.com No Proprietary Web-based Annotation software for annotating contents in Web pages, videos, images, and other documents into a tiny URL and share it with the like-minded individuals or closed groups
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.
Marky Yes Yes No No Yes Yes Yes Chrome, Firefox No GPL 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. Admins 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.
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
OurStickys Yes Yes Yes No No No No Chrome OurStickys is a FREE Chrome Extension for annotations directly on the browser. You can share the notes with multiple users. The company will soon release a version that will allow users to easily join channels and share sticky notes easier between groups as well as the ability to receive notifications directly on the browser when a new note is received.
Pixorize Yes Yes Yes Yes No No Chrome, via pixorize.com No Proprietary Pixorize is the browser-based image annotation platform where users can upload, annotate, and share images online. The webapp includes an annotation editor supporting a variety of annotations and rich text formatting, a viewer supporting interactive annotations on hover, and a search/browser to find public annotations by name. All Pixorize images can be embedded in other pages as a HTML iFrame.
Pundit Yes No Yes No Yes No Chrome, HTML Embed Yes AGPL 3.0[7] It's a suite of two Chrome Extensions for web annotation (Pundit Annotator and Pundit Annotator Pro) and a web application to review and manage annotations. Supports highlight and comment of text fragments in web pages. Supports the creation of semantic annotations using text fragments, whole web pages, Linked Open Data entities (e.g. DBpedia.org). The semantic annotator comes with a default ontology of predicates. Pundit can also be Embedded in HTML pages.
scrible Yes Yes Yes No Yes No Yes No Proprietary 500MB archive storage in free version. Annotations do not always appear at same horizontal position in archived version.
Wallabag[8] Yes No No No Yes No Yes Via Wallabag website only Yes MIT[9] Self-hosted or paid version available. Archived version of page (which is used for annotation) does not always preserve formatting of original page.
Txtpen Yes Yes Yes Yes Yes Yes Yes Chrome, HTML Embed Proprietary World's first W3C compliant web-annotation service. A platform where publishers have full control over what is displayed on their websites.
yellow pen No No No No Yes No No Browser extension for Google Chrome. You can point out important information in long webpages by highlighting text with your mouse. And you can share this highlighted version of page (with special short link) in social media, e--mail, IM etc. or just bookmark it. (By Marker.to)

Discontinued web annotation systems

  • An early version of the Mosaic browser was tested with collaborative annotation feature in 1993[10] but never passed the test state.
  • The earliest web annotation system was probably CritLink, developed in 1997-98 by Ka-Ping Yee of the University of California.[11] 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.[12]
  • Delicious was 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.
  • Wikalong was 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.[13][14]
  • 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.[15]
  • Stickis, launched in 2006, focused primarily on tight-knit communities, and allowed them to create a blog of annotations.
  • stet was the Gplv3 comment system.[16]
  • 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[17] and the web annotation side of it was shut down two years later.[18]
  • ShiftSpace, started in 2008, was a tool for artistic and political subversion and reimagining of websites - development stopped in 2011.
  • Blerp, launched in 2009, was a multimedia, extensible tool for annotating web pages with widgets viewable by any other Blerp user.
  • Google Sidewiki, launched in 2009, 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.

The Hypothes.is Project has provided a more comprehensive survey of previous web annotation efforts

See also


  1. ^ Doug Schepers. "Web Annotation Architecture". W3C. Retrieved 29 July 2016. 
  2. ^ See A.nnotate notifications
  3. ^ Inc., Axiom Networks. "Axiom - Annotate your digital documents". www.axiomnetworks.ca. 
  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. ^ "License - Pundit". Pundit. Retrieved 2016-01-27. 
  8. ^ "Wallabag.org". 
  9. ^ "Wallabag GitHub repository". 
  10. ^ Andreessen, Marc (1993-05-31). "group annotation server guinea pigs?". webhistory.org. Retrieved 2017-11-08. 
  11. ^ Yee, Ka-Ping (2002). "CritLink: Advanced Hyperlinks Enable Public Annotation on the Web". CiteSeerX: 
  12. ^ Third Voice Trails Off, Wired News, April 4, 2001
  13. ^ Wikalong Firefox Addon, Oct 1, 2006
  14. ^ "SEO – SEO-Optimierung". www.wikalong.org. 
  15. ^ Farewell Fleck.com, "The Next Web", May 10, 2010
  16. ^ "Comment system". Free Software Foundation. 11 May 2011. Retrieved 28 July 2016. 
  17. ^ "Box acquires Crocodoc to turn all those docs you upload into HTML5 masterpieces". VentureBeat. 9 May 2013. Retrieved 12 June 2016. 
  18. ^ "Box is Shutting Down Crocodoc Personal and Webnotes on November 1". VentureBeat. 5 August 2015. Retrieved 12 June 2016. 

Further reading