Copied from linked post:

I’m very happy to announce the release of htmx 2.0. This release ends support for Internet Explorer and tightens up some
defaults, but does not change most of the core functionality or the core API of the library.

Note that we are not marking 2.0 as latest in NPM
because we do not want to force-upgrade users who are relying on non-versioned CDN URLs for htmx. Instead, 1.x will
remain latest and the 2.0 line will remain next until Jan 1, 2025. The website, however, will reference 2.0.

Major Changes

• All extensions have been moved out of the core repository to their own repo
  and website: https://extensions.htmx.org. They are now all versioned individually and can be developed outside of
  the normal (slow) htmx release cadence.

  • Most 1.x extensions will work with 2.x, however the SSE extension did have a break and must be upgraded.
  • The older extensions remain in the /dist/ext directory so as to not break the URLs of CDNs like unpkg, but please
    move to the new extension URLs going forward

• We removed the deprecated hx-sse and hx-ws attributes in favor of the extensions, which were available and
  recommended in 1.x.

• HTTP DELETE requests now use parameters, rather than form encoded bodies, for their payload (This is in accordance w/ the spec.)

• We now provide specific files in /dist for the various JavaScript module styles:

  • ESM Modules: /dist/htmx.esm.js
  • AMD Modules: /dist/htmx.amd.js
  • CJS Modules: /dist/htmx.cjs.js
  • The /dist/htmx.js file continues to be browser-loadable

• The hx-on attribute, with its special syntax, has been removed in favor of the less-hacky hx-on: syntax.

Minor Changes

• We made some default changes:
  • htmx.config.scrollBehavior was changed to 'instant' from 'smooth'
  • As mentioned previously, DELETE requests now use query parameters, rather than a form-encoded body. This can
    be reverted by setting htmx.methodsThatUseUrlParams to the value ['get'],
  • htmx.config.selfRequestsOnly now defaults to true rather than false

Features

Not much, really:

• The selectAndSwap() internal API method was replaced with the public (and much better) swap() method
• Web Component support has been improved dramatically
• And the biggest feature of this release: the website now supports dark mode! (Thanks @pokonski!)

A complete upgrade guide can be found here:

htmx 1.x -> 2.x Migration Guide

If you require IE compatibility, the 1.x will continue to be supported for the foreseeable future.