Whoa this is a big one! 6.4.0 brings all the data loading and mutation APIs over from Remix. Here's a quick high level overview, but it's recommended you go check out the docs, especially the feature overview and the tutorial.

New APIs

• Create your router with createMemoryRouter
• Render your router with <RouterProvider>
• Load data with a Route loader and mutate with a Route action
• Handle errors with Route errorElement
• Defer non-critical data with defer and Await

react-router-dom APIs

• Create your router with createBrowserRouter/createHashRouter
• Submit data with the new <Form> component
• Perform in-page data loads and mutations with useFetcher()
• Defer non-critical data with defer and Await
• Manage scroll position with <ScrollRestoration>
• Perform path-relative navigations with <Link relative="path"> (#9160)

Bug Fixes

• Path resolution is now trailing slash agnostic (#8861)
• useLocation returns the scoped location inside a <Routes location> component (#9094)
• Respect the <Link replace> prop if it is defined (#8779)