A favicon  /ˈfævɪkɒn/ (short for Favorite icon), also known as a shortcut icon, Web site icon, URL icon, or bookmark icon, is a file containing one or more small icons, most commonly 16×16 pixels, associated with a particular Web site or Web page. A web designer can create such an icon and install it into a Web site (or Web page) by several means, and graphical web browsers will then make use of it. Browsers that provide favicon support typically display a page's favicon in the browser's address 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 on the tab, and site-specific browsers use the favicon as desktop icon.

In March 1999, Microsoft released Internet Explorer 5 which supported favicons for the first time. Originally, the favicon was a file called favicon.ico placed in the root directory (e.g., http://en.wikipedia.org/favicon.ico) of a web site. It was used in Internet Explorer's favorites (bookmarks) and next to the URL in the address bar if the page was bookmarked. A side effect was that the number of visitors who have bookmarked the page could be estimated by the requests of the favicon. This technique has become obsolete since all modern browsers support the favicon without bookmarking.