HTMX

JavaScript library that brings AJAX, CSS transitions, WebSockets, and Server-Sent Events directly into HTML via declarative attributes. Interactive interfaces are built by adding attributes like hx-post or hx-swap to any element, without writing custom JavaScript. It extends hypertext so any element can issue HTTP requests, any event can trigger them, and any DOM region can be updated from the response.

Adopted alongside server-rendered frameworks such as Django, Rails, or Flask. Backed by sponsors including JetBrains, Craft CMS, and ButterCMS. The library is small, dependency-free, and can be dropped in with a single script tag and no build step. It follows the HATEOAS model, with the server returning HTML fragments rather than JSON, contrasting with React and other SPA approaches.

Key features:

• Declarative AJAX, PUT, PATCH, DELETE from any element via attributes
• WebSockets and SSE support for real-time updates
• CSS transitions for swap animations
• Extensions for Alpine, Web Components, and custom behavior
• Polling, lazy loading, and infinite scroll patterns

Teams add interactivity to server-rendered apps without a heavy SPA stack: inline forms, live search, partial page updates, and progressive enhancement. It pairs well with backend frameworks that render HTML and keeps logic on the server.