Epiphany is the default web browser in elementary OS as of the Loki release. For the default browser in Freya and earlier, use "Midori". For other web browsers, use other tags.
As of elementary OS's 2016 Loki release, Epiphany is the operating system's default web browser. Prior elementary OS releases used midori. In other operating systems, the browser is known as "Web", following a 2012 change.