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.