A means of classifying and categorizing data on the web through collaborative efforts from the online community. This is more commonly known as (though not strictly synonymous to) 'tagging'.

Instead of using a centralized form of classification, users are encouraged to assign freely chosen keywords (called tags) to pieces of information or data, a process known as tagging. Examples of web services that use tagging are flickr, del.icio.us, digg, stumbleupon