Below is a collection of some UI libraries to check out. One of the best things you can do as a software developer is become familiar with tools available to you. A lot of the time you don't need to build a component from scratch, there will be a viable one to use with a flexible usage license.
Many of these advertise themselves as a "Design System" – essentially a cohesive set of components designed to be modular and consistent to facilitate building delightful web experiences. They often have high standards for accessibility as well.
You can think of them as providing a set of primitives that you can then use as the building blocks for building webpages with. If unfamiliar with these concepts, check out https://www.figma.com/design-systems (opens in a new tab) to find out more.
Atlaskit (opens in a new tab)
Atlassian's official UI library, built according to the Atlassian Design System.
MUI (opens in a new tab)
MUI offers a comprehensive suite of UI tools to help you ship new features faster. Start with Material UI, our fully-loaded component library, or bring your own design system to our production-ready components.
Radix UI (opens in a new tab)
An open-source UI component library for building high-quality, accessible design systems and web apps.