hydrateFallbackElement

If you are using Server-Side Rendering and you are leveraging partial hydration, then you can specify an Element/Component to render for non-hydrated routes during the initial hydration of the application.

If you do not wish to specify a React element (i.e., hydrateFallbackElement={<MyFallback />}) you may specify an HydrateFallback component instead (i.e., HydrateFallback={MyFallback}) and React Router will call createElement for you internally. This feature only works if using a data router, see Picking a Router

let router = createBrowserRouter(
  [
    {
      id: "root",
      path: "/",
      loader: rootLoader,
      Component: Root,
      children: [
        {
          id: "invoice",
          path: "invoices/:id",
          loader: loadInvoice,
          Component: Invoice,
          HydrateFallback: InvoiceSkeleton,
        },
      ],
    },
  ],
  {
    future: {
      v7_partialHydration: true,
    },
    hydrationData: {
      root: {
        /*...*/
      },
      // No hydration data provided for the `invoice` route
    },
  }
);

There is no default fallback and it will just render null at that route level, so it is recommended that you always provide your own fallback element.