diff --git a/app/models/user.rb b/app/models/user.rb
index 50a88d2b..b3b5bee5 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -72,7 +72,8 @@ class User < ApplicationRecord
             format:      { with: SCREEN_NAME_REGEX, message: I18n.t("activerecord.validation.user.screen_name.format") },
             length:      { minimum: 1, maximum: 16 },
             uniqueness:  { case_sensitive: false },
-            screen_name: true
+            screen_name: true,
+            read_only: true
 
   mount_uploader :profile_picture, ProfilePictureUploader, mount_on: :profile_picture_file_name
   process_in_background :profile_picture
diff --git a/app/validators/read_only_validator.rb b/app/validators/read_only_validator.rb
new file mode 100644
index 00000000..b9b1301b
--- /dev/null
+++ b/app/validators/read_only_validator.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class ReadOnlyValidator < ActiveModel::EachValidator
+  def validate_each(record, attribute, value)
+    return unless Retrospring::Config.readonly?
+    return if value == record.public_send(:"#{attribute}_was")
+
+    record.errors.add(attribute, message: I18n.t("errors.read_only_mode"))
+  end
+end