diff --git a/lib/mv/constants.ex b/lib/mv/constants.ex
index 334bcc1..7bfb07b 100644
--- a/lib/mv/constants.ex
+++ b/lib/mv/constants.ex
@@ -18,5 +18,17 @@ defmodule Mv.Constants do
     :postal_code
   ]
 
+  @custom_field_prefix "custom_field_"
+
   def member_fields, do: @member_fields
+
+  @doc """
+  Returns the prefix used for custom field keys in field visibility maps.
+
+  ## Examples
+
+      iex> Mv.Constants.custom_field_prefix()
+      "custom_field_"
+  """
+  def custom_field_prefix, do: @custom_field_prefix
 end
diff --git a/lib/mv_web/live/components/field_visibility_dropdown_component.ex b/lib/mv_web/live/components/field_visibility_dropdown_component.ex
index 574262c..642273c 100644
--- a/lib/mv_web/live/components/field_visibility_dropdown_component.ex
+++ b/lib/mv_web/live/components/field_visibility_dropdown_component.ex
@@ -131,17 +131,21 @@ defmodule MvWeb.Components.FieldVisibilityDropdownComponent do
   defp extract_member_field_keys(nil), do: []
 
   defp extract_member_field_keys(fields) do
+    prefix = Mv.Constants.custom_field_prefix()
+
     Enum.filter(fields, fn field ->
       is_atom(field) ||
-        (is_binary(field) && not String.starts_with?(field, "custom_field_"))
+        (is_binary(field) && not String.starts_with?(field, prefix))
     end)
   end
 
   defp extract_custom_field_keys(nil), do: []
 
   defp extract_custom_field_keys(fields) do
+    prefix = Mv.Constants.custom_field_prefix()
+
     Enum.filter(fields, fn field ->
-      is_binary(field) && String.starts_with?(field, "custom_field_")
+      is_binary(field) && String.starts_with?(field, prefix)
     end)
   end
 
@@ -157,7 +161,7 @@ defmodule MvWeb.Components.FieldVisibilityDropdownComponent do
   end
 
   defp format_custom_field_label(field_string, custom_fields) do
-    id = String.trim_leading(field_string, "custom_field_")
+    id = String.trim_leading(field_string, Mv.Constants.custom_field_prefix())
     find_custom_field_name(id, field_string, custom_fields)
   end
 
diff --git a/lib/mv_web/live/member_live/index.ex b/lib/mv_web/live/member_live/index.ex
index f379ede..ad4a4a9 100644
--- a/lib/mv_web/live/member_live/index.ex
+++ b/lib/mv_web/live/member_live/index.ex
@@ -37,7 +37,7 @@ defmodule MvWeb.MemberLive.Index do
   alias MvWeb.MemberLive.Index.FieldVisibility
 
   # Prefix used in sort field names for custom fields (e.g., "custom_field_<id>")
-  @custom_field_prefix "custom_field_"
+  @custom_field_prefix Mv.Constants.custom_field_prefix()
 
   # Member fields that are loaded for the overview
   # Uses constants from Mv.Constants to ensure consistency
@@ -796,7 +796,7 @@ defmodule MvWeb.MemberLive.Index do
   # Format: "custom_field_<id>" -> <id>
   defp extract_custom_field_ids(visible_custom_fields) do
     Enum.map(visible_custom_fields, fn field_string ->
-      case String.split(field_string, "custom_field_") do
+      case String.split(field_string, @custom_field_prefix) do
         ["", id] -> id
         _ -> nil
       end
diff --git a/lib/mv_web/live/member_live/index/field_visibility.ex b/lib/mv_web/live/member_live/index/field_visibility.ex
index 8dd36fc..c9c8bd6 100644
--- a/lib/mv_web/live/member_live/index/field_visibility.ex
+++ b/lib/mv_web/live/member_live/index/field_visibility.ex
@@ -155,9 +155,11 @@ defmodule MvWeb.MemberLive.Index.FieldVisibility do
   """
   @spec get_visible_custom_fields(%{String.t() => boolean()}) :: [String.t()]
   def get_visible_custom_fields(field_selection) when is_map(field_selection) do
+    prefix = Mv.Constants.custom_field_prefix()
+
     field_selection
     |> Enum.filter(fn {field_string, visible} ->
-      visible && String.starts_with?(field_string, "custom_field_")
+      visible && String.starts_with?(field_string, prefix)
     end)
     |> Enum.map(fn {field_string, _visible} -> field_string end)
   end
@@ -188,8 +190,10 @@ defmodule MvWeb.MemberLive.Index.FieldVisibility do
 
   # Gets custom field visibility (all custom fields with show_in_overview=true are visible)
   defp get_custom_field_visibility(custom_fields) do
+    prefix = Mv.Constants.custom_field_prefix()
+
     Enum.reduce(custom_fields, %{}, fn custom_field, acc ->
-      field_string = "custom_field_#{custom_field.id}"
+      field_string = "#{prefix}#{custom_field.id}"
       visible = Map.get(custom_field, :show_in_overview, true)
       Map.put(acc, field_string, visible)
     end)
@@ -218,7 +222,7 @@ defmodule MvWeb.MemberLive.Index.FieldVisibility do
 
   # Converts field string to atom (for member fields) or keeps as string (for custom fields)
   defp to_field_identifier(field_string) when is_binary(field_string) do
-    if String.starts_with?(field_string, "custom_field_") do
+    if String.starts_with?(field_string, Mv.Constants.custom_field_prefix()) do
       field_string
     else
       try do