A front-end developer creates websites and applications using web languages such as HTML, CSS, and JavaScript that allow users to access and interact with the site or app. When you visit a website, the design elements you see were created by a front-end developer. Front-end developers create user interfaces (UI). UI is the graphical layout of an application that determines what each part of a site or application does and how it will look. "I've always found crafting polished user interactions that surprise and delight users to be the most rewarding and engaging task," says Mari Batilando, a software engineer at Meta. "In order to do this, you need to both have an eye for detail and a rock-solid understanding of the platform." If someone wanted to build a website, they might hire a front-end developer to create the site's layout. The front-end developer determines where to place images, what the navigation should look like, and how to present the site. Much of their work involves ensuring the appearance and layout of the site or application is easy to navigate and intuitive for the user.