Anonymous

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.

Installation

Add the plugin to your auth config

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

auth.ts

import { betterAuth } from "better-auth"
import { anonymous } from "better-auth/plugins"
 
export const auth = betterAuth({
    // ... other config options
    plugins: [
        anonymous() 
    ]
})

Migrate the database

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

npx @better-auth/cli migrate

See the Schema section to add the fields manually.

Add the client plugin

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

auth-client.ts

import { createAuthClient } from "better-auth/client"
import { anonymousClient } from "better-auth/client/plugins"
 
const authClient =  createAuthClient({
    plugins: [
        anonymousClient()
    ]
})

Usage

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

example.ts

const user = await authClient.signIn.anonymous()

Link Account

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

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

auth.ts

import { betterAuth } from "better-auth"
 
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.

example.ts

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

Options

emailDomainName: The domain name to use when generating an email address for anonymous users. Defaults to the domain name of the current site.

auth.ts

import { betterAuth } from "better-auth"
 
export const auth = betterAuth({
    plugins: [
        anonymous({
            emailDomainName: "example.com"
        })
    ]
})

onLinkAccount: 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.
disableDeleteAnonymousUser: By default, the anonymous user is deleted when the account is linked to a new authentication method. Set this option to true to disable this behavior.

Schema

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

Field Name	Type	Key	Description
isAnonymous	boolean		Indicates whether the user is anonymous.

Username

Username plugin

Phone Number

Phone number plugin

Username

Phone Number

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