A Tag Cloud (Or Weighted List in Visual Design) Is a Visual Depiction of Content Tags Used

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Tag clouds

A tag cloud with terms related to Web 2.0 /

A tag cloud (or weighted list in visual design) is a visual depiction of content tags used on a website. Often, more frequently used tags are depicted in a larger font or otherwise emphasized, while the displayed order is generally alphabetical. Thus both finding a tag by alphabet and by popularity is possible. Selecting a single tag within a tag cloud will generally lead to a collection of items that are associated with that tag. Examples of in-real-use tag clouds (like zoom clouds, or heat maps) can be found on the MicroFormats-Wiki.

The first widespread use of tag clouds was on the photo sharing website Flickr, created by Flickr co-founder and interaction designer Stewart Butterfield. That implementation was based on Jim Flanagan's Search Referral Zeitgeist, a visualization of Web site referrers. Tag clouds have also been popularised by Del.icio.us and Technorati, among others.

The first published appearance of a tag cloud can be attributed to the "subconscious files" in Douglas Coupland's Microserfs (1995). In Lester Leaps Out, the Welsh poet Doug Lang uses the same logic of weighted texts to create a graphical word-map of jazz music. The poem appears in his book, Magic Fire Chevrolet(1980).

Definition of a tag cloud

A tag cloud is a set of related tags with corresponding weights. Typical tag clouds have between 30 and 150 tags. The weights are represented using font sizes or other visual clues. Meanwhile, histograms or pie charts are most commonly used to represent approximately a dozen different weights. Hence, tag clouds can represent many more weights, though less accurately so. Also, frequently, tag clouds are interactive: tags are hyperlinks typically allowing the user to drill down on the data.

Types of tag clouds

There are three main types of tag cloud applications in social software, distinguished by their meaning rather than appearance. In the first type, there is a tag cloud for each item whereas in the second type, we have global tag clouds where the frequencies are aggregated over all items and users.

In the first type, size represents the number of times that tag has been applied to a single item. This is useful as a means of displaying metadata about an item that has been democratically 'voted' on and where precise results are not desired. A good example of this is Last. fm, which uses this method as a means of displaying the genre with which an artist or track has been tagged.

In the second, more commonly used type, size represents the number of items to which a tag has been applied, as a presentation of each tag's popularity. Examples of this type of tag cloud are used on the image-hosting service Flickr and the blog aggregator Technorati.

In the third type, tags are used as a categorization method for content items. Tags are represented in a cloud where larger tags represent the quantity of content items in that category.

Visual appearance

Tags clouds are typically represented using inline HTML elements. The tags can appear in alphabetical order, in a random order, they can be sorted by weight, and so on. Some prefer to cluster the tags semantically so that similar tags will appear near each other. Heuristics can be used to reduce the size of the tag cloud whether or not we are trying to cluster the tags.