microsoft/fluentui

Fluent UI Web is Microsoft's open source library of ready-made user interface components for building web applications. A UI component library is a collection of pre-built building blocks, buttons, dropdowns, input fields, dialogs, navigation menus, and so on, styled and coded to a consistent design language, so developers do not have to design and build each element from scratch. Fluent is Microsoft's design language, the same visual system used in Microsoft 365 products like Word and Excel and in the Edge browser. The repository contains three separate projects that can be used independently or combined. The first is Fluent UI React v9, the current, forward-looking version built with modern React, used internally by Microsoft 365. The second is Fluent UI React v8, the mature, widely deployed previous version, still supported and used by Office products. The third is Fluent UI Web Components, a framework-agnostic implementation based on the Web Components standard, used in Microsoft Edge. All three are written in TypeScript and published separately on npm. Developers building enterprise web applications on React would reach for Fluent UI when they want their product to look and feel consistent with Microsoft's ecosystem, when they need accessibility built in by default, or when they want to save time by not designing every UI element from scratch. Organizations already using Microsoft 365 or building add-ins and integrations for Microsoft products are the natural audience. You can mix v9 and v8 components in the same project to migrate gradually without a big-bang rewrite.