Oat is described as 'Ultra-lightweight HTML + CSS, semantic UI component library with zero dependencies. No framework, build, or dev complexity. Just include the tiny CSS and JS files and you are good to go building decent looking web applications with most commonly needed components and' and is a CSS Framework in the development category. There are more than 50 alternatives to Oat for a variety of platforms, including Web-based, Self-Hosted, JavaScript, Mac and Windows apps. The best Oat alternative is Bootstrap, which is both free and Open Source. Other great apps like Oat are Bulma, Semantic UI, Foundation and UIkit.