Gmelius is a free browser extension available for Google Chrome, Mozilla Firefox and Opera that customises the look and feel of web mail service Gmail. The extension gives the possibility to Gmail users to determine which interface elements they wish to display in their inbox, as well as how they want to use them. Gmelius is well known for proposing a cleaner and customizable user interface to Gmail's new look; the page format was made compulsory in April 2012.