A favicon, short for 'favorite icon', is the small square image that represents a website across the browser interface. It appears in browser tabs, next to bookmarks, in the history list, and increasingly in search engine results next to a site's listing. Though tiny, the favicon is an important element of brand recognition and a marker of a polished, trustworthy site.
Historically, favicons were a single 16x16 pixel ICO file at the site root, but modern requirements are more involved. Different contexts call for different sizes - browser tabs, high-resolution displays, mobile home-screen icons, and platform-specific touch icons - so sites typically provide a set of icons in multiple sizes and formats, declared in the HTML head with link elements or a web app manifest.
Favicons now carry SEO-adjacent value because search engines display them beside results on mobile and sometimes desktop. A clear, recognizable favicon helps a listing stand out and reinforces brand identity at the moment a user scans the results page. Search engines have guidelines: the favicon must be a square, a multiple of 48 pixels, and associated with the site's homepage.
Practical best practices include using a simple, high-contrast design that remains legible at very small sizes, providing SVG or multiple raster sizes for crisp rendering across devices, and hosting the icon consistently. Overly detailed logos usually become an unreadable blur at favicon dimensions, so a simplified mark or single letter often works better than a full logo.