A favicon (short for favorites icon), also known as a website icon, page icon or urlicon, is an icon associated with a particular website or webpage. A web designer can create such icons in several ways and many recent web browsers can then make use of them. Browsers that support them may display them in the browser's URL bar, next to the site's name in lists of bookmarks, and next to the page's title in a tabbed document interface. Some operating systems, like Windows, will also often use the favicon for Internet shortcuts to sites placed on the desktopcitation needed or in other directories.
Use
The original means of defining a favicon was by placing a file called favicon.ico in the root directory of a web server. This would then automatically be used in Internet Explorer's favorites (bookmarks) display. Later, however, a more flexible system was created using HTML to indicate the location of an icon for any given page. This is achieved by adding two link elements in the <head> section of the document as detailed below. In this way any appropriately sized (16×16 pixels or larger) image can be used and, although many still use the ICO format, other browsers (though not all versions of Microsoft's Internet Explorer) now also support the PNG and animated GIF image formats.
Most modern browsers implement both methods. Because of this web servers receive many requests for the file "favicon.ico" even if it doesn't exist. This may annoy web server administrators by creating many server log entries and unnecessarily loading the disk, CPU, and network. Another common problem is that the favicons may disappear if the browser's cache is emptied.citation needed
Internet Explorer originally only used favicons for bookmarks (for instance MSIE 6.0), which created a minor privacy concern in that a site owner could tell how many people had bookmarked their site by checking the access logs to see how many people downloaded the favicon.ico file. This is becoming less of an issue since newer versions of Internet Explorer (e.g. 7.0) and most other browsers also display the favicon in the address bar on every visit.
Standardization
The original favicon feature was created by Microsoft for Internet Explorer which would request a favicon from a set URL (/favicon.ico) on every website. Microsoft's supported format for the link tag did not conform to the World Wide Web Consortium (W3C) HTML recommendation [1] because:
- The
rel attribute must contain a space-delimited list of link types, so a two-word link type would not be understood correctly by conforming web browsers.
- The ".ico" file format (a raster format used for icons on Microsoft Windows) did not have a registered MIME type and wasn't likely to be automatically understood by most web browsers. In 2003, however, the format was registered with the Internet Assigned Numbers Authority (IANA) under the MIME type image/vnd.microsoft.icon, eliminating the first part of this problem.
- The use of a reserved location on a website conflicts with the Architecture of the World Wide Web and is known as link squatting or URI squatting.
The Mozilla web browser added support for favicons in a way that conformed to web standards through the use of rel="icon" and letting web designers add favicons in any supported graphics format, e.g. <link rel="icon" type="image/png" href="/path/image.png"/>. Most web browsers have since added support for this feature and is generally used for all new content. In cases where favicons are not in bookmarks such as non-http urls like those that begin with irc:// or javascript: the default document icon is used, unless the browser has an option or extension[2] that enables choosing a favicon manually for those urls.
References
External links
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