Supabase Auth now supports Anonymous Sign-ins

2024-04-17

7 minute read

Supabase Auth now supports anonymous sign-ins, one of our most-requested features by the community.

Anonymous sign-ins can be used to create temporary users who haven’t signed up for your application yet. This lowers the friction for new users to try out your product since they don’t have to provide any signup credentials.

Enabling Anonymous sign-ins

You can enable anonymous sign-ins for your project today from the dashboard:

For local development, upgrade your Supabase CLI and add the config to the config.toml file:


_10
[auth]
_10
enable_anonymous_sign_ins = true

You can create an anonymous user through the Javascript, Flutter or Swift SDKs today. Here’s how you can create an anonymous user using supabase-js .


_10
const { data, error } = await supabase
_10
.auth
_10
.signInAnonymously()

Terminology

Profiles created with anonymous sign-ins are also authenticated!

Once you call .signInAnonymously() you have moved the user into an authentication flow, and we treat them like a signed in user:

Restricting access for anonymous users

Like a permanent user, anonymous users are persisted in the auth.users table:

idroleemailis_anonymous
e053e470-afa1-4625-8963-37adb862fd11authenticatedNULLtrue
5563108e-ac81-4063-9288-4f3db068efa1authenticated[email protected]false

An anonymous user can be identified by the is_anonymous claim returned in the user’s JWT, which is accessible from your Row Level Security policies (RLS). This is helpful if you want to limit access to certain features in your application.

For example, let’s say that we have an online forum where users can create and read posts.

Given this table to store the posts:


_10
create table public.posts (
_10
id serial primary key,
_10
name text not null,
_10
description text
_10
);

If we only want to allow permanent users to create posts, we can check if the user is anonymous by inspecting the JWT select auth.jwt() ->> 'is_anonymous'.

Using this function in an RLS policy:


_10
create policy "Only permanent users can create posts"
_10
on public.posts
_10
for insert
_10
to authenticated -- Note: user is still authenticated
_10
with check (
_10
(select auth.jwt() ->> 'is_anonymous')::boolean is false
_10
);

RLS gives us full flexibility to create a variety of rules.

For example, to allow read access for permanent users for all posts and limit anonymous users to posts created today:


_12
create policy "Limit access to anonymous users"
_12
on public.posts
_12
for select
_12
to authenticated -- Note: user is still authenticated
_12
using (
_12
case
_12
when (select (auth.jwt() ->> 'is_anonymous'))::boolean is true
_12
then (created_at >= current_date)
_12
else
_12
true
_12
end
_12
);

Convert an anonymous user to a permanent user

At some point, an anonymous user may decide they want to create a post. This is where we prompt them to sign up for an account which converts them to a permanent user.

Supabase Auth provides 2 ways to achieve this:

  1. Link an email or phone identity
  2. Link an OAuth identity

To link an email or phone identity:


_10
const { data, error } = await supabase
_10
.auth
_10
.updateUser({ email })

To link an OAuth identity to an anonymous user, you need to enable manual linking for your project. Learn about how identity linking works with Supabase Auth.

Once enabled, you can call the linkIdentity() method:


_10
const { data, error } = await supabase
_10
.auth
_10
.linkIdentity({ provider: 'google' })

Impersonating an anonymous user

When creating RLS policies to differentiate access for an anonymous user, you can leverage the user impersonation feature in the SQL editor to test out your policies:

Database role settings in the SQL editor. You can impersonate an anonymous user by selecting the user from the dropdown.

The user management screen provides an option to filter by anonymous users, which can help to know how many anonymous users have been created.

Filtering by anonymous users on the Users page.

What’s next

Managing anonymous users can be tricky, especially when you have a lot of visitors to your site. We’re working on an “automatic clean-up” option to delete anonymous users that have been inactive for more than 30 days. In the meantime, since anonymous users are stored in the auth schema in your database, you can clean up orphaned anonymous users by running the following query:


_10
-- deletes anonymous users created more than 30 days ago
_10
delete from auth.users
_10
where is_anonymous is true and created_at < now() - interval '30 days';

We are also working on a linter to check your RLS policies and highlight those that allow anonymous users access - stay tuned for updates later this month!

Getting started

Share this article

Build in a weekend, scale to millions