A favicon (short for favorites icon), also known as a website icon, shortcut icon, url icon, or bookmark icon is an icon associated with a particular website or webpage. A web designer can create such an icon and install it into a website (or webpage) by several means, and most graphical web browsers will then make use of it. Browsers that provide favicon support typically display a page's favicon in the browser's URL bar and next to the page's name in a list of bookmarks. Browsers that support a tabbed document interface typically show a page's favicon next to the page's title. The Microsoft Windows Shell uses favicons to represent "Internet shortcuts" to web pages.
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 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.
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.
relattribute must contain a space-delimited list of link types, so a two-word link type would not be understood correctly by conforming web browsers. (viz. rel="shortcut icon")
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.
. Most web browsers have since added support for this feature, and it is generally used for all new content.