diff --git a/WeeNu.py b/WeeNu.py
index 5cf151a..698d27e 100644
--- a/WeeNu.py
+++ b/WeeNu.py
@@ -1,75 +1,83 @@
 import rumps
 from datetime import datetime
 import webbrowser
+import os
 
 def get_week_number():
-    """
-    Calculate the current week number according to the ISO 8601 standard,
-    which is used in Sweden.
-    """
     today = datetime.now()
     week_number = today.isocalendar()[1]
     return week_number
 
+class PrefixFormatter:
+    def __init__(self):
+        self.prefix_formats = self.load_prefixes_from_file()
+        self.current_format = self.load_format()
+
+    def format_with_week(self, week_number):
+        self.current_format_formatted = f"{self.current_format} {week_number}"
+        return self.current_format_formatted
+
+    def save_format(self, format_str):
+        try:
+            with open('user_settings', 'w') as f:
+                f.write(format_str)
+                self.current_format = format_str
+        except IOError as e:
+            rumps.alert(f"Error saving current prefix format: {e}")
+
+    def load_format(self):
+        if not os.path.exists('user_settings'):
+            return self.prefix_formats[0]  # Return the first format if the file doesn't exist
+        try:
+            with open('user_settings', 'r') as f:
+                format_str = f.read().strip()
+                if format_str in self.prefix_formats:
+                    return format_str
+        except IOError as e:
+            rumps.alert(f"Error loading prefix format: {e}")
+        return self.prefix_formats[0]
+
+    def load_prefixes_from_file(self):
+        try:
+            with open('prefix_list', 'r') as file:
+                prefixes = [line.strip() for line in file.readlines()]
+        except IOError as e:
+            raise Exception(f"Error reading file: 'prefix_list'")
+        return prefixes
+
 class WeeNu(rumps.App):
     def __init__(self):
         super(WeeNu, self).__init__("WeeNu")
-        self.title_format = "w. {week_number}"
+        self.prefix_formatter = PrefixFormatter()
 
-        # Version info
-        self.menu = ["WeeNu v0.1", None]
-        
-        # Creating a submenu for format toggling
-        self.settings_menu = rumps.MenuItem("Settings")
-        self.toggle_week_prefix_item = rumps.MenuItem("Show prefix", callback=self.toggle_format)
-        
-        self.settings_menu.add(self.toggle_week_prefix_item)
+        self.menu = ["WeeNu v0.2", None]
 
-        # Initializing the menu item's state to True
-        self.toggle_week_prefix_item.state = True
+        self.format_menu = rumps.MenuItem("Prefix")
+        for format_option in self.prefix_formatter.prefix_formats:
+            menu_item = rumps.MenuItem(format_option, callback=self.change_prefix_format)
+            menu_item.state = format_option == self.prefix_formatter.current_format
+            self.format_menu.add(menu_item)
 
-        # Add a divider/separator here
-        self.menu = ["Manual update", self.settings_menu, None]  # 'None' acts as a separator
-        
-        # Add a GitHub link menu item
+        self.menu.add(self.format_menu)
+        self.menu.add(None)
         self.github_link_item = rumps.MenuItem("About WeeNu", callback=self.open_github)
         self.menu.add(self.github_link_item)
 
         self.update_title()
 
-    @rumps.timer(60)  # Update every 60 seconds
+    @rumps.timer(60)
     def update_title(self, _=None):
-        """
-        Updates the menu bar title with the current week number, according to the selected format.
-        """
         week_number = get_week_number()
-        self.title = self.title_format.format(week_number=week_number)
+        self.title = self.prefix_formatter.format_with_week(week_number)
 
-    @rumps.clicked("Manual update")
-    def on_update(self, _):
-        """
-        Manually updates the week number when the 'Update' menu item is clicked.
-        """
+    def change_prefix_format(self, sender):
+        literal_format = sender.title
+        self.prefix_formatter.save_format(literal_format)
+        for item in self.format_menu.values():
+            item.state = item.title == literal_format
         self.update_title()
 
-    def toggle_format(self, sender):
-        """
-        Toggles the title format and the checkmark state based on the current state.
-        """
-        # Toggle the state and adjust the format based on the new state
-        sender.state = not sender.state
-        if sender.state:
-            self.title_format = "w. {week_number}"
-            sender.title = "Hide prefix"
-        else:
-            self.title_format = "{week_number}"
-            sender.title = "Show prefix"
-        self.update_title()
-    
     def open_github(self, _):
-        """
-        Opens the GitHub repository URL in the default web browser.
-        """
         webbrowser.open('https://github.com/mullweisser/mac-weenu')
 
 if __name__ == "__main__":
diff --git a/prefix_list b/prefix_list
new file mode 100644
index 0000000..2c257b6
--- /dev/null
+++ b/prefix_list
@@ -0,0 +1,11 @@
+Week
+WK.
+Wk.
+wk.
+W.
+w.
+WK
+Wk
+wk
+W
+w
\ No newline at end of file
diff --git a/user_settings b/user_settings
new file mode 100644
index 0000000..dc7d5fb
--- /dev/null
+++ b/user_settings
@@ -0,0 +1 @@
+Week
\ No newline at end of file