The ingenious engine of web dev simplicity goes all-in with the Fetch API, native streaming, Idiomorph DOM merging, and more.

InfoWorld is a source of news, analysis, and commentary on technology trends, IT strategies, and business innovation. With a focus on enterprise technology and digital transformation, InfoWorld offers insights and guidance for IT decision-makers, software developers, and technology professionals. From  articles on cloud computing and cybersecurity to product reviews and industry trends, InfoWorld helps readers navigate the complexities of modern IT environments and make informed decisions to drive business success.

InfoWorld

HTMX 4.0 is a major release that replaces the legacy XHR transport layer with the modern Fetch API, enabling native streaming of HTML fragments via ReadableStream. Key changes include: Idiomorph DOM morphing algorithm now bundled in core (was an extension in 2.x), explicit prop inheritance replacing implicit inheritance, removal of the brittle localStorage history engine, status-specific error swapping syntax (e.g. hx-status:404), a new <hx-partial> tag for cleaner multi-target server responses, and native View Transitions API integration. Despite HTMX 2.0 being declared the final version, the team jumped to 4.0 to honor the 'no 3.0' promise while delivering a refactor that adds more power with less complexity, keeping the library at ~14KB.

HTMX 4.0: Hypermedia finds a new gear

<p>What stands out to me is how much of this is about execution layer improvements (Fetch, streams, DOM morphing) rather than API surface changes. It’s still HTML-over-the-wire, just with a much more capable runtime.</p>
