htmx 4.0.0 has been released! ~ htmx (https://cdn.jsdelivr.net) (https://four.htmx.org/sitemap-index.xml) (2026-08-28-htmx-4.0.0-is-released.html) (../favicon.svg) (htmx — Atom feed) (https://four.htmx.org/atom.xml) (htmx — RSS feed) (https://four.htmx.org/rss.xml) (../_astro/Layout.0JkR7Gfp.css) (../_astro/_..DYquaUGr.css) (../_astro/content.BQGi-kHu.css)                                                                                                                 (https://four.htmx.org/) < / -  > -  htmx  home    (/) v4 (https://htmx.org) v2 (https://v1.htmx.org) v1     (https://four.htmx.org/docs) docs   (https://four.htmx.org/docs/morphing-swaps-guide) Morphing Guide  (https://four.htmx.org/docs/htmx-events-guide) htmx Events Guide  (https://four.htmx.org/docs/hx-live-guide) hx-live Programmers Guide  (https://four.htmx.org/docs/extension-authoring-guide) htmx Extension Authoring Guide  (https://four.htmx.org/docs/hcon-guide) HCON  (https://four.htmx.org/docs/htmax) htmax  (https://four.htmx.org/docs/editor-support) Editor Support     (https://four.htmx.org/reference) reference  (https://four.htmx.org/patterns) patterns  (https://four.htmx.org/extensions) extensions  (https://four.htmx.org/essays) essays  (https://four.htmx.org/game) game  (https://four.htmx.org/about) about     Open Search Ctrl K ⌘ K     (https://four.htmx.org/discord) (Join the Discord community)   (https://github.com/bigskysoftware/htmx) (View source code on GitHub)             (https://four.htmx.org/docs) docs (https://four.htmx.org/docs/morphing-swaps-guide) Morphing Guide  (https://four.htmx.org/docs/htmx-events-guide) htmx Events Guide  (https://four.htmx.org/docs/hx-live-guide) hx-live Programmers Guide  (https://four.htmx.org/docs/extension-authoring-guide) htmx Extension Authoring Guide  (https://four.htmx.org/docs/hcon-guide) HCON  (https://four.htmx.org/docs/htmax) htmax  (https://four.htmx.org/docs/editor-support) Editor Support    (https://four.htmx.org/reference) reference  (https://four.htmx.org/patterns) patterns  (https://four.htmx.org/extensions) extensions  (https://four.htmx.org/essays) essays  (https://four.htmx.org/game) game  (https://four.htmx.org/about) about    (https://four.htmx.org/discord) (Join the Discord community)  Discord  (https://github.com/bigskysoftware/htmx) (View source code on GitHub)  GitHub     On this page  (2026-08-28-htmx-4.0.0-is-released.html#htmx-400-release) htmx 4.0.0 Release (2026-08-28-htmx-4.0.0-is-released.html#major-changes) Major Changes  (2026-08-28-htmx-4.0.0-is-released.html#new-features) New Features  (2026-08-28-htmx-4.0.0-is-released.html#upgrading) Upgrading  (2026-08-28-htmx-4.0.0-is-released.html#installing) Installing  (2026-08-28-htmx-4.0.0-is-released.html#llms) LLMs  (2026-08-28-htmx-4.0.0-is-released.html#conclusion) Conclusion  (2026-08-28-htmx-4.0.0-is-released.html#upgrade-music) Upgrade Music       (https://github.com/bigskysoftware/htmx/edit/four-dev/www/src/content/announcements/2026-08-28-htmx-4.0.0-is-released.md)  Edit page    (https://four.htmx.org/announcements)  Announcements  (https://four.htmx.org/) Home  / (https://four.htmx.org/announcements) Announcements  / htmx 4.0.0 has been released!    htmx 4.0.0 has been released!  (Copy page content as Markdown)  Copy page    (https://four.htmx.org/announcements/2026-08-28-htmx-4.0.0-is-released.md)   View as Markdown  Open this page as Markdown   For LLMs (https://four.htmx.org/llms.txt)   llms.txt  htmx overview for LLMs   (https://four.htmx.org/llms-full.txt)   llms-full.txt  Complete htmx docs for LLMs        Release announcement, 2026-08-28.  On this page (2026-08-28-htmx-4.0.0-is-released.html#htmx-400-release) htmx 4.0.0 Release (2026-08-28-htmx-4.0.0-is-released.html#major-changes) Major Changes  (2026-08-28-htmx-4.0.0-is-released.html#new-features) New Features  (2026-08-28-htmx-4.0.0-is-released.html#upgrading) Upgrading  (2026-08-28-htmx-4.0.0-is-released.html#installing) Installing  (2026-08-28-htmx-4.0.0-is-released.html#llms) LLMs  (2026-08-28-htmx-4.0.0-is-released.html#conclusion) Conclusion  (2026-08-28-htmx-4.0.0-is-released.html#upgrade-music) Upgrade Music       (htmx 4 land cruiser)  (2026-08-28-htmx-4.0.0-is-released.html#htmx-400-release) htmx 4.0.0 Release  The htmx team is very happy to announce the release of htmx 4.0.0!  This is the culmination of 8 months of work (plus
a (https://four.htmx.org/game) game ) and we are very happy with the results. The idea of htmx 4 started to germinate when I decided to create (https://fixiproject.org) fixi and, in doing so, got
more familiar with the fetch() API and async programming in JavaScript.  (htmx had always
used (https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest) XMLHttpRequest due
to backwards compatibility issues.) One chance evening I was contacted by Christian, who had some interesting ideas
around (https://four.htmx.org/docs#streaming-html) streaming HTML that
got me thinking that moving the internals to fetch() would simplify things for him and for the library in general.After a bit of work I managed to get Michael and Alex on board, and we were off to the races. Development has been very smooth. We started a port of fixi + the htmx test suite. Over time, we rediscovered why htmx
did many of the things that it did and moved our new implementation closer and closer to the old one. At this point
the behavioral differences between 2.x and 4.x are relatively small and where they do diverge we have made explicit
choices that we feel will put htmx-based applications in a good spot for
being (https://www.youtube.com/watch?v=lASLZ9TgXyc) 100-year web services  Note that we are not marking 4.0 as (https://docs.npmjs.com/cli/v10/commands/npm-dist-tag#purpose) latest  in NPM
because we do not want to force-upgrade users who are relying on non-versioned CDN URLs for htmx. Instead, 2.x will
remain latest and the 4.0 line will remain next until some point in early 2027. The website, however, will reference 4.0. (2026-08-28-htmx-4.0.0-is-released.html#major-changes) Major Changes  As mentioned above, htmx 4, from a user’s viewpoint, is almost identical to htmx 2. There are three major changes: Attribute inheritance is now explicit by default rather than implicit by default (this is the biggest upgrade item) The htmx event names have been standardized & cleaned up. Some advanced users may need to change the events they
listen for. History support now does not use localStorage by default (which was a cause of many support headaches). Most people
won’t notice this at all.  Internally, we migrated from XMLHttpRequest to fetch() but that should be transparent for most users of htmx. (2026-08-28-htmx-4.0.0-is-released.html#attribute-inheritance) Attribute Inheritance  In htmx 2 many attributes were “inherited” by default. This allows you to place attributes on parent elements and
their behavior will apply to child elements. This behavior, which came from
the (https://intercoolerjs.org) intercooler.js days, was inspired by CSS and, unsurprisingly, worked out about the same
as CSS: powerful but difficult to understand at times. In htmx 4 attributes are not inherited unless you (https://four.htmx.org/docs#attribute-inheritance) explicitly say so by adding an :inherited after the attribute name: (Copy to clipboard)       <!-- htmx 2 -->  < div hx-confirm = "Are you sure?" >  < button hx-delete = "/item/1" >Delete</ button >  </ div >   <!-- htmx 4 -->  < div hx-confirm:inherited = "Are you sure?" >  < button hx-delete = "/item/1" >Delete</ button >  </ div >    This will be the largest upgrade burden in migrating from htmx 2 to htmx 4. To make things easier, we have provided
a (https://four.htmx.org/docs#upgrade-checker) command line tool to find places you need to mark as inherited. Note that attributes like hx-disinherit , etc. are no longer required and should be removed. (2026-08-28-htmx-4.0.0-is-released.html#events) Events  The events triggered by htmx 2 had grown organically over the life of the library and were not particularly well
organized, making it difficult to know exactly which event was fired when. In htmx 4, all events now follow htmx:phase:action[:sub-action] : htmx 2 htmx 4   htmx:beforeRequest  htmx:before:request   htmx:afterRequest  htmx:after:request   htmx:beforeSwap  htmx:before:swap   htmx:afterSwap  htmx:after:swap   htmx:configRequest  htmx:config:request     In addition, the following changes were made: Most error events collapse into (https://four.htmx.org/reference/events/htmx-error) htmx:error  . HTTP error responses fire (https://four.htmx.org/reference/events/htmx-response-error) htmx:response:error  . The htmx:xhr:* events are removed. htmx 4 uses fetch() . The htmx:validation:* events are removed in favor of native browser form validation.  The full table is in (https://four.htmx.org/docs/whats-new-in-htmx-4) What’s New in htmx 4 . The command line upgrade checker flags old event names in hx-on attributes and in your JavaScript where it can find
them. (2026-08-28-htmx-4.0.0-is-released.html#history) History  History support has always been included in htmx, allowing you to implement back-button aware actions with simple
attributes. In htmx 2, a cache in localStorage was used to snapshot pages for restoration. Unfortunately a large
source of issues was that this snapshot could include DOM mutations by 3rd party JavaScript libraries. When the page was
restored, those mutations remained but the underlying JavaScript logic was not. htmx 4 does not cache pages in localStorage . On back navigation htmx re-fetches the page and swaps it into <body> ,
or into the [hx-history-elt] element if one is present. This allows 3rd party JavaScript libraries to “just work” in
most cases and, with good request caching, is very fast. If you want local caching instead, we now ship a very complete (https://four.htmx.org/extensions/hx-history-cache) hx-history-cache  extension that restores history from sessionStorage and is designed to integrate well with scripting solutions like
Alpine.js, etc. (2026-08-28-htmx-4.0.0-is-released.html#new-features) New Features  There are two big new features in htmx 4, both of which we are really excited about: (2026-08-28-htmx-4.0.0-is-released.html#morph-swaps) Morph Swaps  We now support (https://four.htmx.org/docs#morphing-swaps) morphing swaps out of the box with htmx.  I created (https://github.com/bigskysoftware/idiomorph) idiomorph and
nearly included it in htmx 2.x but decided against it.  In htmx 4, Michael has done great work improving on that
algorithm and integrating it seamlessly into htmx. (2026-08-28-htmx-4.0.0-is-released.html#hx-partial) <hx-partial>   Another major new feature is the <hx-partial> tag.  This tag is similar to (https://four.htmx.org/docs#out-of-band-swaps) out-of-band swaps ,
but is much clearer when you want to do something beyond just replacing a single element with a new version of itself: (Copy to clipboard)       < hx-partial hx-target = "#messages" hx-swap = "beforeend" >  < div >New message</ div >  </ hx-partial >  < hx-partial hx-target = "#count" >  < span >5</ span >  </ hx-partial >    (2026-08-28-htmx-4.0.0-is-released.html#extensions) Extensions  Much of the excitement in htmx 4 is in the extensions.  Switching to fetch() internally let us rethink how extensions
can and should work, and sparked the creation (and recreation) of many new extensions, for example: hx-preload - preload content (e.g. on mouseover ) to speed requests up hx-download - native, fetch-based file downloads hx-alpine-compat - smooths over compatibility issues between htmx and (https://alpinejs.dev/) Alpine.js  hx-history-cache - caches history in sessionStorage , provides Alpine.js compatibility  Additionally, there are three new or updated streaming HTML extensions: (https://four.htmx.org/extensions/hx-sse) hx-sse  streams over text/event-stream . (https://four.htmx.org/extensions/hx-ws) hx-ws  streams and sends over WebSockets. (https://four.htmx.org/extensions/hx-multipart) hx-multipart  streams over multipart/mixed   Finally, we decided it was time to try our hand at our own small front-end scripting solution that tightly integrates with htmx. (https://four.htmx.org/extensions/hx-live) hx-live  is inspired by Alpine.js, (https://jquery.com/) jQuery and (https://hyperscript.org) hyperscript , and makes front end scripting pleasant and fun.  It even supports what we are calling DOM-based, HATEOAS-friendly reactivity. There is a new (https://four.htmx.org/docs/htmax) htmax.js  bundle in the distribution which packages htmx with the most popular of these in a single file if you don’t want to think about which ones you want to pick. (2026-08-28-htmx-4.0.0-is-released.html#upgrading) Upgrading  For a complete upgrade guide see (https://four.htmx.org/docs/whats-new-in-htmx-4) What’s New in htmx 4 . As mentioned earlier, we are providing an upgrade tool to help you: (Copy to clipboard)       $ npx htmx.org@4.0.0 upgrade-check -- ./templates   File extensions: .html, .php, .js, .ts, .jinja, .jinja2, .j2, .erb, .hbs  Use --ext to add more (e.g.  --ext .vue --ext .svelte )   Scanning 1 file ( s ) ...   Found 8 issue ( s )  in 1 of 1 file ( s ) .  templates/index.html:1: [inheritance] hx-headers needs :inherited suffix ( descendant on line 3 has hx-delete ) ( this looks like a CSRF token ;  without :inherited the header does not reach child elements and the server rejects the request )  templates/index.html:2: [inheritance] hx-target needs :inherited suffix ( descendant on line 3 has hx-delete )  templates/index.html:2: [inheritance] hx-confirm needs :inherited suffix ( descendant on line 3 has hx-delete )  templates/index.html:3: [renamed-attr] hx-disable - > rename to hx-ignore ( hx-disable now means 'disable during request' )  templates/index.html:4: [removed-attr] hx-vars is removed - > use hx-vals with js: prefix  templates/index.html:4: [removed-attr] hx-prompt is removed - > load the hx-prompt extension to keep the same syntax  templates/index.html:9: [old-event] old event name  "htmx:afterRequest" - > "htmx:after:request"  templates/index.html:9: [old-api]  htmx.addClass () is removed - > use  element.classList.add ()    We are also shipping an (https://four.htmx.org/docs/editor-support#ai-coding-assistants) agent skill to assist in upgrading (2026-08-28-htmx-4.0.0-is-released.html#installing) Installing  htmx 4.0 can be installed via a package manager referencing version 4.0.0 , or can be linked via a CDN: (Copy to clipboard)        < script src = "https://unpkg.com/htmx.org@4.0.0/dist/htmx.min.js" ></ script >    or (https://unpkg.com/htmx.org@4.0.0/dist/htmx.min.js) Downloaded  (2026-08-28-htmx-4.0.0-is-released.html#llms) LLMs  Like it or not, a lot of people are using LLMs and we are providing the following skills files for LLMs: (https://raw.githubusercontent.com/bigskysoftware/htmx/v4.0.0/dist/skills/htmx-guidance.md) htmx-guidance  - core htmx skills for developing with htmx 4 (https://raw.githubusercontent.com/bigskysoftware/htmx/v4.0.0/dist/skills/htmx-debugging.md) htmx-debugging  - diagnosing htmx issues during dev (https://raw.githubusercontent.com/bigskysoftware/htmx/v4.0.0/dist/skills/htmx-extension-authoring.md) htmx-extension-authoring  - writing and debugging htmx 4 extensions (https://raw.githubusercontent.com/bigskysoftware/htmx/v4.0.0/dist/skills/htmx-upgrade-from-htmx2.md) htmx-upgrade-from-htmx2  - migrating a codebase from htmx 2.x to 4.x  (Let’s leave aside if releasing a new version of a library in the LLM era is a good or bad thing!) (2026-08-28-htmx-4.0.0-is-released.html#conclusion) Conclusion  We hope you enjoy htmx 4.  htmx 2 will continue to be supported indefinitely so don’t feel any pressure to upgrade. I’d like to thank the following people for all their help with this release: (https://github.com/MichaelWest22) Michael West - Incredible teammate & grug-brained developer (https://github.com/scriptogre) Christian Tanul - Inspired htmx 4 & led the streaming & live extensions (https://github.com/alexpetros) Alex Petros - For keeping the ship on an even keel Stephen Mitchell - The genius behind the (https://four.htmx.org/game) game  Stu Kennedy - Our WebSockets expert André Ahlert Jr. - Providing IDE & Editor Support Dien Hoa Truong - For kicking the tires on early htmx 4 and helping fix many bugs  (2026-08-28-htmx-4.0.0-is-released.html#upgrade-music) Upgrade Music  Wouldn’t be an htmx update without upgrade music: (Playtime Is Over)        Links (https://four.htmx.org/docs) (Go to /docs) docs  (https://four.htmx.org/reference) (Go to /reference) reference  (https://four.htmx.org/patterns) (Go to /patterns) patterns  (https://four.htmx.org/extensions) (Go to /extensions) extensions  (https://four.htmx.org/essays) (Go to /essays) essays  (https://four.htmx.org/game) (Go to /game) game  (https://four.htmx.org/about) (Go to /about) about    Community (https://four.htmx.org/discord) (Go to /discord)   Discord  (https://github.com/bigskysoftware/htmx) (Go to https://github.com/bigskysoftware/htmx)   GitHub  (https://x.com/htmx_org) (Go to https://x.com/htmx_org)   @htmx_org  (https://www.reddit.com/r/htmx/) (Go to https://www.reddit.com/r/htmx/)   Reddit  (https://stackoverflow.com/questions/tagged/htmx) (Go to https://stackoverflow.com/questions/tagged/htmx)   Stack Overflow    Resources (https://four.htmx.org/interviews) (Go to /interviews)   Interviews  (https://four.htmx.org/podcasts) (Go to /podcasts)   Podcasts  (https://four.htmx.org/memes) (Go to /memes)   Memes  (https://hypermedia.systems) (Go to https://hypermedia.systems)   Book  (https://four.htmx.org/rss.xml) (Go to /rss.xml)   RSS    Haiku javascript fatigue:longing for a hypertextalready in hand    © 2026· (https://bigsky.software) (Go to Big Sky Software's website) Big Sky Software         Search documentation (Search documentation...) esc   No results found Try a different search term    ↑ ↓ to navigate    to select   outside to close