Wt (pronounced as witty) is a C++ library for developing web applications. The API is widget-centric and uses well-tested patterns of desktop GUI development tailored to the web. To the developer, it offers abstraction of many web-specific implementation details, including client-server protocols (HTTP, Ajax, WebSockets), and frees the developer from tedious JavaScript manipulations of HTML and dealing with cross-browser issues. Instead, with Wt, you can focus on actual functionality with a rich set of feature-complete widgets. Unlike old-school page-based frameworks or current-day single-page JavaScript "frameworks", Wt allows you to create stateful applications that are at the same time highly interactive (using WebSockets and Ajax for everything) but still support plain HTML browsers or web crawlers using automatic graceful degradation or progressive enhancement. Things that are natural and simple with Wt would require an impractical amount of development effort otherwise: switching widgets using animations, while retaining clean URLs and browser navigation functions, or having a persistent chat widget open throughout the entire application, that even works in legacy browsers like Microsoft Internet Explorer 6. The library comes with an application server that acts as a stand-alone Http(s)/WebSocket server or integrates through FastCGI with other web servers.