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Better Auth integrates with SvelteKit through a server hook handler and a Svelte-aware auth client. Before you start, make sure you have a Better Auth instance configured. If you haven’t done that yet, check out the installation.

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Mount the handler

Register Better Auth inside SvelteKit’s hooks.server.ts using svelteKitHandler from better-auth/svelte-kit. The handler intercepts requests to the auth base path and forwards them to Better Auth; all other requests are passed through to resolve.
hooks.server.ts
import { auth } from "$lib/auth";
import { svelteKitHandler } from "better-auth/svelte-kit";
import { building } from "$app/environment";

export async function handle({ event, resolve }) {
  return svelteKitHandler({ event, resolve, auth, building });
}
The building flag prevents Better Auth from running during SvelteKit’s static build step.

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Populate session data in locals

svelteKitHandler does not automatically populate event.locals. If you need access to the current user in server load functions, form actions, or endpoints, fetch the session and assign it in the handle hook:
hooks.server.ts
import { auth } from "$lib/auth";
import { svelteKitHandler } from "better-auth/svelte-kit";
import { building } from "$app/environment";

export async function handle({ event, resolve }) {
  const session = await auth.api.getSession({
    headers: event.request.headers,
  });

  if (session) {
    event.locals.session = session.session;
    event.locals.user = session.user;
  }

  return svelteKitHandler({ event, resolve, auth, building });
}
Declare the session and user types on App.Locals in your src/app.d.ts file so TypeScript recognises them throughout your app.

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Server action cookies

To ensure cookies are set correctly when you call functions like signInEmail or signUpEmail inside a server action, add the sveltekitCookies plugin to your auth instance.
getRequestEvent is available from SvelteKit 2.20.0 and later. Make sure you are on a compatible version.
lib/auth.ts
import { betterAuth } from "better-auth";
import { sveltekitCookies } from "better-auth/svelte-kit";
import { getRequestEvent } from "$app/server";

export const auth = betterAuth({
  // ...your config
  plugins: [sveltekitCookies(getRequestEvent)], // must be the last plugin in the array
});

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Create a client

Create an auth client instance and export it from a shared module. Import from better-auth/svelte to get Svelte-specific reactive stores.
lib/auth-client.ts
import { createAuthClient } from "better-auth/svelte";

export const authClient = createAuthClient({
  // optional client configuration
});
The client uses nano-stores internally, so reactive values update automatically when session state changes (e.g. after sign-in or sign-out).

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useSession store

authClient.useSession() returns a nano-store. Subscribe to it with the $ prefix in Svelte components.
+page.svelte
<script lang="ts">
  import { authClient } from "$lib/auth-client";

  const session = authClient.useSession();
</script>

<div>
  {#if $session.data}
    <p>{$session.data.user.name}</p>
    <button on:click={async () => await authClient.signOut()}>
      Sign out
    </button>
  {:else}
    <button
      on:click={async () =>
        await authClient.signIn.social({ provider: "github" })}
    >
      Continue with GitHub
    </button>
  {/if}
</div>

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Server-side session access in load functions

Because you populated event.locals in the hook, you can read the session directly from locals in any server load function without an additional database call.
routes/dashboard/+page.server.ts
import { redirect } from "@sveltejs/kit";
import type { PageServerLoad } from "./$types";

export const load: PageServerLoad = async ({ locals }) => {
  if (!locals.session) {
    throw redirect(302, "/sign-in");
  }

  return {
    user: locals.user,
  };
};