diff --git a/MareSynchronos/UI/MainUi.cs b/MareSynchronos/UI/MainUi.cs
index e61100d..ae1333b 100644
--- a/MareSynchronos/UI/MainUi.cs
+++ b/MareSynchronos/UI/MainUi.cs
@@ -7,7 +7,6 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Net.Mime;
 using System.Numerics;
 using System.Threading.Tasks;
 using MareSynchronos.API;
@@ -84,10 +83,15 @@ namespace MareSynchronos.UI
             }
             else
             {
-                string error = _configuration.FullPause ? "Disconnected" : _apiController.ServerAlive ? "Unauthorized" : "Service unavailable";
+                var error = _configuration.FullPause ? "Disconnected" 
+                    : !_apiController.ServerAlive 
+                        ? "Service unavailable" 
+                        : !_apiController.ServerSupportsThisClient 
+                            ? "Service version mismatch" 
+                            : "Unauthorized";
                 ImGui.TextColored(ImGuiColors.DalamudRed, $"No UID ({error})");
                 ImGui.SetWindowFontScale(1.0f);
-                if (_apiController.ServerAlive && !_configuration.FullPause)
+                if (_apiController.ServerAlive && !_configuration.FullPause && _apiController.ServerSupportsThisClient)
                 {
                     ImGui.PushStyleColor(ImGuiCol.Text, ImGuiColors.DalamudRed);
                     UiShared.TextWrapped("Your account is not present on the service anymore or you are banned.");
@@ -101,6 +105,11 @@ namespace MareSynchronos.UI
                         _configuration.Save();
                         SwitchFromMainUiToIntro?.Invoke();
                     }
+                } else if (!_apiController.ServerSupportsThisClient)
+                {
+                    ImGui.PushStyleColor(ImGuiCol.Text, ImGuiColors.DalamudRed);
+                    UiShared.TextWrapped("The server or your client is outdated. If the client has recently been updated for breaking service changes, the service must follow suit.");
+                    ImGui.PopStyleColor();
                 }
             }
 
diff --git a/MareSynchronos/WebAPI/ApiController.Connectivity.cs b/MareSynchronos/WebAPI/ApiController.Connectivity.cs
index 0e23e67..df4fac2 100644
--- a/MareSynchronos/WebAPI/ApiController.Connectivity.cs
+++ b/MareSynchronos/WebAPI/ApiController.Connectivity.cs
@@ -18,6 +18,7 @@ namespace MareSynchronos.WebAPI
 #if DEBUG
         public const string MainServer = "darkarchons Debug Server (Dev Server (CH))";
         public const string MainServiceUri = "wss://darkarchon.internet-box.ch:5000";
+        public readonly int[] SupportedServerVersions = { 1 };
 #else
         public const string MainServer = "Lunae Crescere Incipientis (Central Server EU)";
         public const string MainServiceUri = "to be defined";
@@ -37,10 +38,10 @@ namespace MareSynchronos.WebAPI
         private CancellationTokenSource? _uploadCancellationTokenSource;
 
         private HubConnection? _userHub;
-        private LoggedInUserDto? _loggedInUser;
-        public bool IsModerator => (_loggedInUser?.IsAdmin ?? false) || (_loggedInUser?.IsModerator ?? false);
+        private ConnectionDto? _connectionDto;
+        public bool IsModerator => (_connectionDto?.IsAdmin ?? false) || (_connectionDto?.IsModerator ?? false);
 
-        public bool IsAdmin => _loggedInUser?.IsAdmin ?? false;
+        public bool IsAdmin => _connectionDto?.IsAdmin ?? false;
 
         public ApiController(Configuration pluginConfiguration, DalamudUtil dalamudUtil)
         {
@@ -95,7 +96,7 @@ namespace MareSynchronos.WebAPI
 
         public List<ForbiddenFileDto> AdminForbiddenFiles { get; private set; } = new();
 
-        public bool IsConnected => !string.IsNullOrEmpty(UID);
+        public bool IsConnected => !string.IsNullOrEmpty(UID) && ServerSupportsThisClient;
 
         public bool IsDownloading => CurrentDownloads.Count > 0;
 
@@ -108,11 +109,13 @@ namespace MareSynchronos.WebAPI
         public bool ServerAlive =>
             (_heartbeatHub?.State ?? HubConnectionState.Disconnected) == HubConnectionState.Connected;
 
+        public bool ServerSupportsThisClient => SupportedServerVersions.Contains(_connectionDto?.ServerVersion ?? 0);
+
         public Dictionary<string, string> ServerDictionary => new Dictionary<string, string>() { { MainServiceUri, MainServer } }
             .Concat(_pluginConfiguration.CustomServerList)
             .ToDictionary(k => k.Key, k => k.Value);
 
-        public string UID => _loggedInUser?.UID ?? string.Empty;
+        public string UID => _connectionDto?.UID ?? string.Empty;
 
         private string ApiUri => _pluginConfiguration.ApiUri;
         public int OnlineUsers { get; private set; }
@@ -143,15 +146,17 @@ namespace MareSynchronos.WebAPI
                     await _adminHub.StartAsync(token);
 
                     OnlineUsers = await _userHub.InvokeAsync<int>("GetOnlineUsers", token);
-
+                    _userHub.On<int>("UsersOnline", (count) => OnlineUsers = count);
+                    
                     if (_pluginConfiguration.FullPause)
                     {
-                        _loggedInUser = null;
+                        _connectionDto = null;
                         return;
                     }
 
-                    _loggedInUser = await _heartbeatHub.InvokeAsync<LoggedInUserDto>("Heartbeat", token);
-                    if (!string.IsNullOrEmpty(UID) && !token.IsCancellationRequested) // user is authorized
+                    _connectionDto = await _heartbeatHub.InvokeAsync<ConnectionDto>("Heartbeat", token);
+                    if (!string.IsNullOrEmpty(UID) && !token.IsCancellationRequested 
+                                                   && ServerSupportsThisClient) // user is authorized && server is legit
                     {
                         Logger.Debug("Initializing data");
                         _userHub.On<ClientPairDto, string>("UpdateClientPairs", UpdateLocalClientPairsCallback);
@@ -160,7 +165,6 @@ namespace MareSynchronos.WebAPI
                             (s) => PairedClientOffline?.Invoke(s, EventArgs.Empty));
                         _userHub.On<string>("AddOnlinePairedPlayer",
                             (s) => PairedClientOnline?.Invoke(s, EventArgs.Empty));
-                        _userHub.On<int>("UsersOnline", (count) => OnlineUsers = count);
                         _adminHub.On("ForcedReconnect", UserForcedReconnectCallback);
 
                         PairedClients = await _userHub!.InvokeAsync<List<ClientPairDto>>("GetPairedClients", token);
@@ -239,7 +243,7 @@ namespace MareSynchronos.WebAPI
         {
             Logger.Debug("Connection restored");
             OnlineUsers = _userHub!.InvokeAsync<int>("GetOnlineUsers").Result;
-            _loggedInUser = _heartbeatHub!.InvokeAsync<LoggedInUserDto>("Heartbeat").Result;
+            _connectionDto = _heartbeatHub!.InvokeAsync<ConnectionDto>("Heartbeat").Result;
             Connected?.Invoke(this, EventArgs.Empty);
             return Task.CompletedTask;
         }