Once UI is an open-source design system and component library tailored for Next.js, complemented by a corresponding design system in Figma, featuring a versatile style system, over 100 pre-built UI components, and more than 75 copy-paste blocks to expedite the creation of web applications. It caters to both basic static websites and more intricate applications, offering pre-constructed, ready-to-deploy templates for various needs, including portfolios, documentation sites, blogs, ecommerce platforms, and dashboards, available in both free and Pro versions. The framework promotes a "component-first" approach to development, allowing developers to avoid the tedious task of manually coding with utility-class-heavy styling, which is common in certain CSS frameworks; instead, they can leverage semantic variables and components that utilize design tokens for consistent visual aesthetics. For those familiar with utility-class frameworks or component libraries seeking a quicker development process with reduced dependencies, Once UI streamlines the UI building process, ensuring that design quality and accessibility remain uncompromised. This innovative approach not only enhances productivity but also empowers creators to deliver sophisticated designs effortlessly.