diff --git a/XIVChat Desktop/App.xaml.cs b/XIVChat Desktop/App.xaml.cs
index 895ced4..1b9f8e4 100644
--- a/XIVChat Desktop/App.xaml.cs	
+++ b/XIVChat Desktop/App.xaml.cs	
@@ -31,7 +31,7 @@ namespace XIVChat_Desktop {
 
         public event PropertyChangedEventHandler? PropertyChanged;
 
-        private void Application_Startup(object sender, StartupEventArgs e) {
+        private async void Application_Startup(object sender, StartupEventArgs e) {
             try {
                 this.Config = Configuration.Load() ?? new Configuration();
             } catch (Exception ex) {
@@ -62,12 +62,24 @@ namespace XIVChat_Desktop {
                 )
             );
 
-            var wnd = new MainWindow();
-            this.Window = wnd;
-
             // I guess this gets initialised where you call it the first time, so initialise it on the UI thread
             this.Dispatcher.Invoke(() => { });
 
+            #if RELEASE
+            if (string.IsNullOrWhiteSpace(this.Config.LicenceKey) || !(await LicenceWindow.LicenceInfo(this.Config.LicenceKey)).Valid()) {
+                var lic = new LicenceWindow(null, true);
+                lic.Show();
+                return;
+            }
+            #endif
+
+            this.InitialiseWindow();
+        }
+
+        public void InitialiseWindow() {
+            var wnd = new MainWindow();
+            this.Window = wnd;
+
             wnd.Show();
 
             // initialise a config window to apply all our settings
diff --git a/XIVChat Desktop/Configuration.cs b/XIVChat Desktop/Configuration.cs
index 240c97f..24af0e7 100644
--- a/XIVChat Desktop/Configuration.cs	
+++ b/XIVChat Desktop/Configuration.cs	
@@ -16,6 +16,8 @@ namespace XIVChat_Desktop {
     public class Configuration : INotifyPropertyChanged {
         public event PropertyChangedEventHandler? PropertyChanged;
 
+        public string? LicenceKey { get; set; }
+
         public KeyPair KeyPair { get; set; } = PublicKeyBox.GenerateKeyPair();
 
         public ObservableCollection<SavedServer> Servers { get; set; } = new ObservableCollection<SavedServer>();
diff --git a/XIVChat Desktop/LicenceWindow.xaml b/XIVChat Desktop/LicenceWindow.xaml
new file mode 100644
index 0000000..998d838
--- /dev/null
+++ b/XIVChat Desktop/LicenceWindow.xaml	
@@ -0,0 +1,32 @@
+<Window x:Class="XIVChat_Desktop.LicenceWindow"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:local="clr-namespace:XIVChat_Desktop"
+        xmlns:ui="http://schemas.modernwpf.com/2019"
+        ui:WindowHelper.UseModernWindowStyle="True"
+        mc:Ignorable="d"
+        Title="Licence"
+        WindowStartupLocation="CenterOwner"
+        ContentRendered="LicenceWindow_OnContentRendered"
+        SizeToContent="WidthAndHeight"
+        d:DataContext="{d:DesignInstance local:LicenceWindow}">
+    <StackPanel Margin="8">
+        <ProgressBar x:Name="Loading"
+                     IsIndeterminate="True" />
+        <StackPanel x:Name="LicenceInfoPanel"
+                    Visibility="Collapsed">
+            <TextBlock x:Name="LicenceDescription"
+                       Text="Checking licence..." />
+            <TextBox x:Name="LicenceKey"
+                     Text="{Binding App.Config.LicenceKey}"
+                     ui:ControlHelper.Header="Licence key" />
+            <Button x:Name="CheckButton"
+                    Margin="0,8,0,0"
+                    Content="Check"
+                    Click="Check_Click"
+                    IsEnabled="False" />
+        </StackPanel>
+    </StackPanel>
+</Window>
diff --git a/XIVChat Desktop/LicenceWindow.xaml.cs b/XIVChat Desktop/LicenceWindow.xaml.cs
new file mode 100644
index 0000000..af964aa
--- /dev/null
+++ b/XIVChat Desktop/LicenceWindow.xaml.cs	
@@ -0,0 +1,123 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using System.Windows;
+using Windows.Web.Http;
+using Newtonsoft.Json;
+
+namespace XIVChat_Desktop {
+    public partial class LicenceWindow {
+        public App App => (App)Application.Current;
+
+        private readonly bool startAfterSuccess;
+
+        public LicenceWindow(Window? owner, bool startAfterSuccess) {
+            this.Owner = owner;
+            this.startAfterSuccess = startAfterSuccess;
+            this.InitializeComponent();
+            this.DataContext = this;
+
+            var empty = string.IsNullOrWhiteSpace(this.App.Config.LicenceKey);
+            if (empty) {
+                this.CheckButton.IsEnabled = true;
+                this.LicenceDescription.Text = "No licence key has been supplied. Please enter one.";
+                this.SetLoading(false);
+                return;
+            }
+
+            _ = Task.Run(async () => {
+                await this.Check();
+                this.Dispatch(() => this.SetLoading(false));
+            });
+        }
+
+        private void SetLoading(bool loading) {
+            this.Loading.Visibility = loading ? Visibility.Visible : Visibility.Collapsed;
+            this.LicenceInfoPanel.Visibility = loading ? Visibility.Collapsed : Visibility.Visible;
+        }
+
+        private async Task<bool> Check(bool increment = false) {
+            this.Dispatch(() => this.CheckButton.IsEnabled = false);
+
+            var licence = await LicenceInfo(this.App.Config.LicenceKey!, increment);
+            var valid = licence.Valid();
+
+            this.Dispatch(() => {
+                this.CheckButton.IsEnabled = true;
+                this.LicenceDescription.Text = valid
+                    ? $"Valid licence key for {licence.purchase.email}. Thank you!"
+                    : "Invalid licence key. Please check the key and try again.";
+            });
+
+            return valid;
+        }
+
+        private async void Check_Click(object sender, RoutedEventArgs e) {
+            this.App.Config.Save();
+
+            var valid = await this.Check(true);
+
+            if (!valid || !this.startAfterSuccess) {
+                return;
+            }
+
+            this.App.InitialiseWindow();
+            this.Close();
+        }
+
+        public static async Task<LicenceResponse> LicenceInfo(string key, bool increment = false) {
+            var uri = new Uri("https://api.gumroad.com/v2/licenses/verify");
+            var data = new Dictionary<string, string> {
+                ["product_permalink"] = "kvQIw",
+                ["license_key"] = key,
+                ["increment_uses_count"] = increment ? "true" : "false",
+            };
+
+            var client = new HttpClient();
+            var res = await client.PostAsync(uri, new HttpFormUrlEncodedContent(data));
+            var response = JsonConvert.DeserializeObject<LicenceResponse>(await res.Content.ReadAsStringAsync());
+
+            return response;
+        }
+
+        private void LicenceWindow_OnContentRendered(object? sender, EventArgs e) {
+            this.InvalidateVisual();
+        }
+    }
+
+    public class LicenceResponse {
+        public readonly bool success;
+        public readonly uint uses;
+        public readonly Purchase purchase;
+
+        public LicenceResponse(bool success, uint uses, Purchase purchase) {
+            this.success = success;
+            this.uses = uses;
+            this.purchase = purchase;
+        }
+
+        public bool Valid() {
+            return this.success && !this.purchase.refunded && !this.purchase.chargebacked;
+        }
+    }
+
+    public class Purchase {
+        public readonly string id;
+        public readonly string productName;
+        public readonly DateTime createdAt;
+        public readonly string fullName;
+        public readonly bool refunded;
+        public readonly bool chargebacked;
+        public readonly string email;
+
+        public Purchase(string id, string productName, DateTime createdAt, string fullName, bool refunded, bool chargebacked, string email) {
+            this.id = id;
+            this.productName = productName;
+            this.createdAt = createdAt;
+            this.fullName = fullName;
+            this.refunded = refunded;
+            this.chargebacked = chargebacked;
+            this.email = email;
+        }
+    }
+}
diff --git a/XIVChat Desktop/MainWindow.xaml b/XIVChat Desktop/MainWindow.xaml
index db835c6..0cbb40b 100644
--- a/XIVChat Desktop/MainWindow.xaml	
+++ b/XIVChat Desktop/MainWindow.xaml	
@@ -34,6 +34,8 @@
                 <MenuItem Header="Export"
                           Click="Export_Click" />
                 <Separator />
+                <MenuItem Header="Licence"
+                          Click="Licence_Click" />
                 <MenuItem Header="Configuration"
                           Click="Configuration_Click" />
             </MenuItem>
diff --git a/XIVChat Desktop/MainWindow.xaml.cs b/XIVChat Desktop/MainWindow.xaml.cs
index 9607143..84d6291 100644
--- a/XIVChat Desktop/MainWindow.xaml.cs	
+++ b/XIVChat Desktop/MainWindow.xaml.cs	
@@ -185,5 +185,9 @@ namespace XIVChat_Desktop {
         private void Export_Click(object sender, RoutedEventArgs e) {
             new Export(this).Show();
         }
+
+        private void Licence_Click(object sender, RoutedEventArgs e) {
+            new LicenceWindow(this, false).Show();
+        }
     }
 }