diff --git a/app/controllers/api/v1/extensions_controller.rb b/app/controllers/api/v1/extensions_controller.rb
new file mode 100644
index 0000000000..15e57f945b
--- /dev/null
+++ b/app/controllers/api/v1/extensions_controller.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+require 'mastodon/extension'
+
+class Api::V1::ExtensionsController < Api::BaseController
+  def index
+    render json: Mastodon::Extension.all
+  end
+end
diff --git a/config/routes.rb b/config/routes.rb
index dc93fc6fe6..c0a1fccf0b 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -238,6 +238,8 @@ Rails.application.routes.draw do
           post :unmute
         end
       end
+
+      resources :extensions, only: :list
     end
 
     namespace :web do
diff --git a/lib/mastodon/extensions.rb b/lib/mastodon/extensions.rb
new file mode 100644
index 0000000000..974c8286ba
--- /dev/null
+++ b/lib/mastodon/extensions.rb
@@ -0,0 +1,17 @@
+class Mastodon::Extension
+  @@extensions = []
+
+  def self.register url
+    @extensions << Extension.new(url)
+  end
+
+  def self.all
+    @extensions
+  end
+
+  def initialize url
+    @url = url
+  end
+
+  attr_reader :url
+end