The Anonymous plugin allows users to have an authenticated experience without requiring them to provide an email address, password, OAuth provider, or any other Personally Identifiable Information (PII). Users can later link an authentication method to their account when ready.

To enable anonymous authentication, add the anonymous plugin to your authentication configuration.

```ts title="auth.ts"
import { betterAuth } from "better-auth"
import { anonymous } from "better-auth/plugins" // [!code highlight]

export const auth = betterAuth({
    // ... other config options
    plugins: [
        anonymous() // [!code highlight]
    ]
})
```

Run the migration or generate the schema to add the necessary fields and tables to the database.

<Tabs items={["migrate", "generate"]}>
  <Tab value="migrate">
    ```package-install
    npx auth migrate
    ```
  </Tab>

  <Tab value="generate">
    ```package-install
    npx auth generate
    ```
  </Tab>
</Tabs>

See the [Schema](#schema) section to add the fields manually.

Next, include the anonymous client plugin in your authentication client instance.

```ts title="auth-client.ts"
import { createAuthClient } from "better-auth/client"
import { anonymousClient } from "better-auth/client/plugins" // [!code highlight]

export const authClient = createAuthClient({
    plugins: [
        anonymousClient() // [!code highlight]
    ]
})
```

To sign in a user anonymously, use the signIn.anonymous() method.

import { authClient } from "@/lib/auth-client";

const user = await authClient.signIn.anonymous()

If a user is already signed in anonymously and tries to signIn or signUp with another method, their anonymous activities can be linked to the new account.

To do that you first need to provide onLinkAccount callback to the plugin.

import { betterAuth } from "better-auth"
import { anonymous } from "better-auth/plugins"

export const auth = betterAuth({
    plugins: [
        anonymous({
            onLinkAccount: async ({ anonymousUser, newUser }) => {
               // perform actions like moving the cart items from anonymous user to the new user
            }
        })
    ]

Then when you call signIn or signUp with another method, the onLinkAccount callback will be called. And the anonymousUser will be deleted by default.

import { authClient } from "@/lib/auth-client";

const user = await authClient.signIn.email({
    email,
})

To delete an anonymous user, you can call the /delete-anonymous-user endpoint.

• The anonymous user is deleted by default when the account is linked to a new authentication method.
• Setting disableDeleteAnonymousUser to true will prevent the anonymous user from being able to call the /delete-anonymous-user endpoint.

The domain name to use when generating an email address for anonymous users. If not provided, the default format temp@{id}.com is used.

import { betterAuth } from "better-auth"
import { anonymous } from "better-auth/plugins"

export const auth = betterAuth({
    plugins: [
        anonymous({
            emailDomainName: "example.com" // [!code highlight] -> temp-{id}@example.com
        })
    ]
})

A custom function to generate email addresses for anonymous users. This allows you to define your own email format. The function can be synchronous or asynchronous.

import { betterAuth } from "better-auth"
import { anonymous } from "better-auth/plugins"

export const auth = betterAuth({
    plugins: [
        anonymous({
            generateRandomEmail: () => { // [!code highlight]
                const id = crypto.randomUUID() // [!code highlight]
                return `guest-${id}@example.com` // [!code highlight]
            } // [!code highlight]
        })
    ]
})

• If generateRandomEmail is provided, emailDomainName is ignored.
• You are responsible for ensuring the email is unique to avoid conflicts. The returned email must be in a valid format.

A callback function that is called when an anonymous user links their account to a new authentication method. The callback receives an object with the anonymousUser and the newUser.

By default, when an anonymous user links their account to a new authentication method, the anonymous user record is automatically deleted. If you set this option to true, this automatic deletion will be disabled, and the /delete-anonymous-user endpoint will no longer be accessible to anonymous users.

A callback function that is called to generate a name for the anonymous user. Useful if you want to have random names for anonymous users, or if name is unique in your database.

The anonymous plugin requires an additional field in the user table:

export const anonymousUserTableFields = [ { name: "isAnonymous", type: "boolean", description: "Indicates whether the user is anonymous.", isOptional: true, }, ];