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Astro Integration

Better Auth comes with first class support for Astro. This guide will show you how to integrate Better Auth with Astro.

Before you start, make sure you have a Better Auth instance configured. If you haven't done that yet, check out the installation.

Mount the handler

To enable Better Auth to handle requests, we need to mount the handler to a catch all API route. Create a file inside /pages/api/auth called [...all].ts and add the following code:

pages/api/auth/[...all].ts
import { auth } from "~/auth";
import type { APIRoute } from "astro";
 
export const ALL: APIRoute = async (ctx) => {
	return auth.handler(ctx.request);
};

You can change the path on your better-auth configuration but it's recommended to keep it as /api/auth/[...all]

Create a client

Astro supports multiple frontend frameworks, so you can easily import your client based on the framework you're using.

If you're not using a frontend framework, you can still import the vanilla client.

lib/auth-client.ts
import { createAuthClient } from "better-auth/client"
export const client = createAuthClient()

Auth Middleware

Astro Locals types

To have types for your Astro locals, you need to set it inside the env.d.ts file.

env.d.ts
 
/// <reference path="../.astro/types.d.ts" />
 
declare namespace App {
    // Note: 'import {} from ""' syntax does not work in .d.ts files.
    interface Locals {
        user: import("better-auth").User | null;
        session: import("better-auth").Session | null;
    }
}

Middleware

To protect your routes, you can check if the user is authenticated using the getSession method in middleware and set the user and session data using the Astro locals with the types we set before. Start by creating a middleware.ts file in the root of your project and follow the example below:

middleware.ts
import { auth } from "@/auth";
import { defineMiddleware } from "astro:middleware";
 
export const onRequest = defineMiddleware(async (context, next) => {
    const isAuthed = await auth.api
        .getSession({
            headers: context.request.headers,
        })
 
    if (isAuthed) {
        context.locals.user = isAuthed.user;
        context.locals.session = isAuthed.session;
    } else {
        context.locals.user = null;
        context.locals.session = null;
    }
 
    return next();
});

Getting session on the server inside .astro file

You can use Astro.locals to check if the user has session and get the user data from the server side. Here is an example of how you can get the session inside an .astro file:

---
import { UserCard } from "@/components/user-card";
 
const session = () => {
    if (Astro.locals.session) {
        return Astro.locals.session;
    } else {
        // Redirect to login page if the user is not authenticated
        return Astro.redirect("/login");
    }
}
 
---
 
<UserCard initialSession={session} />
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