diff --git a/config/description.exs b/config/description.exs
index d18649ae8..4d80dd846 100644
--- a/config/description.exs
+++ b/config/description.exs
@@ -1061,6 +1061,18 @@ config :pleroma, :config_description, [
         suggestions: [
           "en"
         ]
+      },
+      %{
+        key: :multitenancy,
+        type: :map,
+        description: "Multitenancy support",
+        children: [
+          %{
+            key: :enabled,
+            type: :boolean,
+            description: "Enables allowing multiple Webfinger domains"
+          },
+        ]
       }
     ]
   },
@@ -3466,5 +3478,5 @@ config :pleroma, :config_description, [
         ]
       }
     ]
-  }
+  },
 ]
diff --git a/docs/configuration/how_to_serve_multiple_domains_for_webfinger.md b/docs/configuration/how_to_serve_multiple_domains_for_webfinger.md
new file mode 100644
index 000000000..5a7a3733f
--- /dev/null
+++ b/docs/configuration/how_to_serve_multiple_domains_for_webfinger.md
@@ -0,0 +1,30 @@
+# How to serve multiple domains for Pleroma user identifiers
+
+It is possible to use multiple domains for WebFinger identifiers. If configured, users can select from the available domains during registration. Domains can be set by instance administrator and can be marked as either public (everyone can choose it) or private (only available when admin creates a user)
+
+## Configuring
+
+### Configuring Pleroma
+
+To enable using multiple domains, append the following to your `prod.secret.exs` or `dev.secret.exs`:
+```elixir
+config :pleroma, :instance, :multitenancy, enabled: true
+```
+
+Creating, updating and deleting domains is available from the admin API.
+
+### Configuring WebFinger domains
+
+If you recall how webfinger queries work, the first step is to query `https://example.org/.well-known/host-meta`, which will contain an URL template.
+
+Therefore, the easiest way to configure the additional domains is to redirect `/.well-known/host-meta` to the domain used by Pleroma.
+
+With nginx, it would be as simple as adding:
+
+```nginx
+location = /.well-known/host-meta {
+       return 301 https://pleroma.example.org$request_uri;
+}
+```
+
+in the additional domain's server block.
diff --git a/lib/pleroma/domain.ex b/lib/pleroma/domain.ex
index d708188ee..cf7efc350 100644
--- a/lib/pleroma/domain.ex
+++ b/lib/pleroma/domain.ex
@@ -19,11 +19,13 @@ defmodule Pleroma.Domain do
     domain
     |> cast(params, [:domain, :public])
     |> validate_required([:domain])
+    |> update_change(:domain, &String.downcase/1)
+    |> unique_constraint(:domain)
   end
 
   def update_changeset(%__MODULE__{} = domain, params \\ %{}) do
     domain
-    |> cast(params, [:domain])
+    |> cast(params, [:public])
   end
 
   def get(id), do: Repo.get(__MODULE__, id)
diff --git a/lib/pleroma/web/admin_api/controllers/domain_controller.ex b/lib/pleroma/web/admin_api/controllers/domain_controller.ex
index 46b039460..cb2b7dd3f 100644
--- a/lib/pleroma/web/admin_api/controllers/domain_controller.ex
+++ b/lib/pleroma/web/admin_api/controllers/domain_controller.ex
@@ -37,11 +37,13 @@ defmodule Pleroma.Web.AdminAPI.DomainController do
   end
 
   def create(%{body_params: params} = conn, _) do
-    domain =
-      params
-      |> Domain.create()
-
-    render(conn, "show.json", domain: domain)
+    with {:domain_not_used, true} <-
+           {:domain_not_used, params[:domain] !== Pleroma.Web.WebFinger.domain()},
+         {:domain, domain} <- Domain.create(params) do
+      render(conn, "show.json", domain: domain)
+    else
+      {:domain_not_used, false} -> {:error, :invalid_domain}
+    end
   end
 
   def update(%{body_params: params} = conn, %{id: id}) do
diff --git a/lib/pleroma/web/mastodon_api/views/instance_view.ex b/lib/pleroma/web/mastodon_api/views/instance_view.ex
index 4ab4ccb74..fa2b467ec 100644
--- a/lib/pleroma/web/mastodon_api/views/instance_view.ex
+++ b/lib/pleroma/web/mastodon_api/views/instance_view.ex
@@ -147,7 +147,7 @@ defmodule Pleroma.Web.MastodonAPI.InstanceView do
   end
 
   defp multitenancy do
-    enabled = Config.get([:multitenancy, :enabled])
+    enabled = Config.get([:instance, :multitenancy, :enabled])
 
     if enabled do
       domains =
diff --git a/lib/pleroma/web/web_finger.ex b/lib/pleroma/web/web_finger.ex
index 49c17e2c3..39e38d25c 100644
--- a/lib/pleroma/web/web_finger.ex
+++ b/lib/pleroma/web/web_finger.ex
@@ -102,7 +102,7 @@ defmodule Pleroma.Web.WebFinger do
     end
   end
 
-  defp domain do
+  def domain do
     Pleroma.Config.get([__MODULE__, :domain]) || Pleroma.Web.Endpoint.host()
   end
 
diff --git a/priv/repo/migrations/20230618190919_create_domains.exs b/priv/repo/migrations/20230618190919_create_domains.exs
index a306c80ee..c97e07326 100644
--- a/priv/repo/migrations/20230618190919_create_domains.exs
+++ b/priv/repo/migrations/20230618190919_create_domains.exs
@@ -3,7 +3,7 @@ defmodule Pleroma.Repo.Migrations.CreateDomains do
 
   def change do
     create_if_not_exists table(:domains) do
-      add(:domain, :string)
+      add(:domain, :citext)
       add(:public, :boolean)
 
       timestamps()