Anonymous Sign-Ins

Enable Anonymous Sign-Ins to build apps which provide users an authenticated experience without requiring users to enter an email address, password, use an OAuth provider or provide any other PII (Personally Identifiable Information). Later, when ready, the user can link an authentication method to their account.

Calling signInAnonymously() creates an anonymous user. It's just like a permanent user, except the user can't access their account if they sign out, clear browsing data, or use another device.

Like permanent users, the authenticated Postgres role will be used when using the Data APIs to access your project. JWTs for these users will have an is_anonymous claim which you can use to distinguish in RLS policies.

This is different from the anon API key which does not create a user and can be used to implement public access to your database as it uses the anonymous Postgres role.

Anonymous sign-ins can be used to build:

• E-commerce applications, such as shopping carts before check-out
• Full-feature demos without collecting personal information
• Temporary or throw-away accounts

Review your existing RLS policies before enabling anonymous sign-ins. Anonymous users use the authenticated role. To distinguish between anonymous users and permanent users, your policies need to check the is_anonymous field of the user's JWT.

See the Access control section for more details.

The Supabase team has received reports of user metadata being cached across unique anonymous users as a result of Next.js static page rendering. For the best user experience, utilize dynamic page rendering.

For self-hosting, you can update your project configuration using the files and environment variables provided. See the local development docs for more details.

Sign in anonymously

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Call the signInAnonymously() method:

import { createClient } from '@supabase/supabase-js'
const supabase = createClient('https://your-project.supabase.co', 'sb_publishable_... or anon key')

// ---cut---
const { data, error } = await supabase.auth.signInAnonymously()

Call the signInAnonymously() method:

await supabase.auth.signInAnonymously();

Call the signInAnonymously() method:

let session = try await supabase.auth.signInAnonymously()

Call the signInAnonymously() method:

supabase.auth.signInAnonymously()

Call the sign_in_anonymously() method:

response = supabase.auth.sign_in_anonymously()

Convert an anonymous user to a permanent user

Converting an anonymous user to a permanent user requires linking an identity to the user. This requires you to enable manual linking in your Supabase project.

Link an email / phone identity

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You can use the updateUser() method to link an email or phone identity to the anonymous user. To add a password for the anonymous user, the user's email or phone number needs to be verified first.

import { createClient } from '@supabase/supabase-js'
const supabase = createClient('https://your-project.supabase.co', 'sb_publishable_... or anon key')

// ---cut---
const { data: updateEmailData, error: updateEmailError } = await supabase.auth.updateUser({
  email: '[email protected]',
})

// verify the user's email by clicking on the email change link
// or entering the 6-digit OTP sent to the email address

// once the user has been verified, update the password
const { data: updatePasswordData, error: updatePasswordError } = await supabase.auth.updateUser({
  password: 'password',
})

You can use the updateUser() method to link an email or phone identity to the anonymous user.

await supabase.auth.updateUser(UserAttributes(email: '[email protected]'));

You can use the update(user:) method to link an email or phone identity to the anonymous user.

try await supabase.auth.update(
  user: UserAttributes(email: "[email protected]")
)

You can use the updateUser() method to link an email or phone identity to the anonymous user.

supabase.auth.updateUser {
    email = "[email protected]"
}

You can use the update_user() method to link an email or phone identity to the anonymous user. To add a password for the anonymous user, the user's email or phone number needs to be verified first.

response = supabase.auth.update_user({
  'email': '[email protected]',
})

# verify the user's email by clicking on the email change link
# or entering the 6-digit OTP sent to the email address

# once the user has been verified, update the password
response = supabase.auth.update_user({
  'password': 'password',
})

Link an OAuth identity

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You can use the linkIdentity() method to link an OAuth identity to the anonymous user.

import { createClient } from '@supabase/supabase-js'
const supabase = createClient('https://your-project.supabase.co', 'sb_publishable_... or anon key')

// ---cut---
const { data, error } = await supabase.auth.linkIdentity({ provider: 'google' })

You can use the linkIdentity() method to link an OAuth identity to the anonymous user.

await supabase.auth.linkIdentity(OAuthProvider.google);

You can use the linkIdentity() method to link an OAuth identity to the anonymous user.

try await supabase.auth.linkIdentity(provider: .google)

You can use the linkIdentity() method to link an OAuth identity to the anonymous user.

supabase.auth.linkIdentity(Google)

You can use the link_identity() method to link an OAuth identity to the anonymous user.

response = supabase.auth.link_identity({'provider': 'google'})

Access control

An anonymous user assumes the authenticated role just like a permanent user. You can use row-level security (RLS) policies to differentiate between an anonymous user and a permanent user by checking for the is_anonymous claim in the JWT returned by auth.jwt():

create policy "Only permanent users can post to the news feed"
on news_feed as restrictive for insert
to authenticated
with check ((select (auth.jwt()->>'is_anonymous')::boolean) is false );

create policy "Anonymous and permanent users can view the news feed"
on news_feed for select
to authenticated
using ( true );

RLS policies are permissive by default, which means that they are combined using an "OR" operator when multiple policies are applied. It is important to construct restrictive policies to ensure that the checks for an anonymous user are always enforced when combined with other policies. Be aware that a single 'restrictive' RLS policy alone will fail unless combined with another policy that returns true, ensuring the combined condition is met.

Resolving identity conflicts

Depending on your application requirements, data conflicts can arise when an anonymous user is converted to a permanent user. For example, in the context of an e-commerce application, an anonymous user would be allowed to add items to the shopping cart without signing up / signing in. When they decide to sign-in to an existing account, you will need to decide how you want to resolve data conflicts in the shopping cart:

1. Overwrite the items in the cart with those in the existing account
2. Overwrite the items in the cart with those from the anonymous user
3. Merge the items in the cart together

Linking an anonymous user to an existing account

In some cases, you may need to link an anonymous user to an existing account rather than creating a new permanent account. This process requires manual handling of potential conflicts. Here's a general approach:

// 1. Sign in anonymously (assuming the user is already signed in anonymously)
const { data: anonData, error: anonError } = await supabase.auth.getSession()

// 2. Attempt to update the user with the existing email
const { data: updateData, error: updateError } = await supabase.auth.updateUser({
  email: '[email protected]',
})

// 3. Handle the error (since the email belongs to an existing user)
if (updateError) {
  console.log('This email belongs to an existing user. Please sign in to that account.')

  // 4. Sign in to the existing account
  const {
    data: { user: existingUser },
    error: signInError,
  } = await supabase.auth.signInWithPassword({
    email: '[email protected]',
    password: 'user_password',
  })

  if (existingUser) {
    // 5. Reassign entities tied to the anonymous user
    // This step will vary based on your specific use case and data model
    const { data: reassignData, error: reassignError } = await supabase
      .from('your_table')
      .update({ user_id: existingUser.id })
      .eq('user_id', anonData.session.user.id)

    // 6. Implement your chosen conflict resolution strategy
    // This could involve merging data, overwriting, or other custom logic
    await resolveDataConflicts(anonData.session.user.id, existingUser.id)
  }
}

// Helper function to resolve data conflicts (implement based on your strategy)
async function resolveDataConflicts(anonymousUserId, existingUserId) {
  // Implement your conflict resolution logic here
  // This could involve ignoring the anonymous user's metadata, overwriting the existing user's metadata, or merging the data of both the anonymous and existing user.
}

Abuse prevention and rate limits

Since anonymous users are stored in your database, bad actors can abuse the endpoint to increase your database size drastically. It is strongly recommended to enable invisible CAPTCHA or Cloudflare Turnstile to prevent abuse for anonymous sign-ins. An IP-based rate limit is enforced at 30 requests per hour which can be modified in your dashboard. You can refer to the full list of rate limits here.

Automatic cleanup

Automatic cleanup of anonymous users is currently not available. Instead, you can delete anonymous users from your project by running the following SQL:

-- deletes anonymous users created more than 30 days ago
delete from auth.users
where is_anonymous is true and created_at < now() - interval '30 days';

Resources

• Supabase - Get started for free
• Supabase JS Client
• Supabase Flutter Client
• Supabase Kotlin Client