diff --git a/ControlR.Agent/Interfaces/IDeviceDataGenerator.cs b/ControlR.Agent/Interfaces/IDeviceDataGenerator.cs
index 5af7fc82..3a58cbb5 100644
--- a/ControlR.Agent/Interfaces/IDeviceDataGenerator.cs
+++ b/ControlR.Agent/Interfaces/IDeviceDataGenerator.cs
@@ -2,14 +2,14 @@
 
 public interface IDeviceDataGenerator
 {
-  Task<DeviceDto> CreateDevice(double cpuUtilization, string deviceId);
+  Task<DeviceDto> CreateDevice(double cpuUtilization, Guid deviceId);
 
   string GetAgentVersion();
 
   List<Drive> GetAllDrives();
 
   DeviceDto GetDeviceBase(
-    string deviceId,
+    Guid deviceId,
     string currentUser,
     List<Drive> drives,
     double usedStorage,
diff --git a/ControlR.Agent/Services/AgentHubConnection.cs b/ControlR.Agent/Services/AgentHubConnection.cs
index 186f3138..0605ba0b 100644
--- a/ControlR.Agent/Services/AgentHubConnection.cs
+++ b/ControlR.Agent/Services/AgentHubConnection.cs
@@ -116,12 +116,9 @@ public Task<Result<AgentAppSettings>> GetAgentAppSettings()
   [SupportedOSPlatform("windows6.0.6000")]
   public Task<WindowsSession[]> GetWindowsSessions()
   {
-    if (environmentHelper.Platform != SystemPlatform.Windows)
-    {
-      return Array.Empty<WindowsSession>().AsTaskResult();
-    }
-
-    return win32Interop.GetActiveSessions().ToArray().AsTaskResult();
+    return environmentHelper.Platform == SystemPlatform.Windows
+      ? win32Interop.GetActiveSessions().ToArray().AsTaskResult()
+      : Array.Empty<WindowsSession>().AsTaskResult();
   }
 
   public Task<Result> ReceiveAgentAppSettings(AgentAppSettings appSettings)
diff --git a/ControlR.Agent/Services/Base/AgentInstallerBase.cs b/ControlR.Agent/Services/Base/AgentInstallerBase.cs
index 2e78d460..d8de2343 100644
--- a/ControlR.Agent/Services/Base/AgentInstallerBase.cs
+++ b/ControlR.Agent/Services/Base/AgentInstallerBase.cs
@@ -27,10 +27,10 @@ protected async Task UpdateAppSettings(Uri? serverUri, string? authorizedKey, st
     logger.LogInformation("Setting server URI to {ServerUri}.", updatedServerUri);
     currentOptions.ServerUri = updatedServerUri;
     
-    if (string.IsNullOrWhiteSpace(currentOptions.DeviceId))
+    if (currentOptions.DeviceId == Guid.Empty)
     {
       logger.LogInformation("DeviceId is empty.  Generating new one.");
-      currentOptions.DeviceId = RandomGenerator.CreateDeviceToken();
+      currentOptions.DeviceId = Guid.NewGuid();
     }
 
     logger.LogInformation("Writing results to disk.");
diff --git a/ControlR.Agent/Services/Base/DeviceDataGeneratorBase.cs b/ControlR.Agent/Services/Base/DeviceDataGeneratorBase.cs
index de67eb2f..a11ce884 100644
--- a/ControlR.Agent/Services/Base/DeviceDataGeneratorBase.cs
+++ b/ControlR.Agent/Services/Base/DeviceDataGeneratorBase.cs
@@ -53,7 +53,7 @@ public List<Drive> GetAllDrives()
     }
 
     public DeviceDto GetDeviceBase(
-        string deviceId, 
+        Guid deviceId, 
         string currentUser, 
         List<Drive> drives, 
         double usedStorage, 
diff --git a/ControlR.Agent/Services/Linux/DeviceGeneratorLinux.cs b/ControlR.Agent/Services/Linux/DeviceGeneratorLinux.cs
index 52a47099..d47c4df4 100644
--- a/ControlR.Agent/Services/Linux/DeviceGeneratorLinux.cs
+++ b/ControlR.Agent/Services/Linux/DeviceGeneratorLinux.cs
@@ -12,7 +12,7 @@ internal class DeviceDataGeneratorLinux(
   private readonly ILogger<DeviceDataGeneratorLinux> _logger = logger;
   private readonly IProcessManager _processInvoker = processInvoker;
 
-  public async Task<DeviceDto> CreateDevice(double cpuUtilization, string deviceId)
+  public async Task<DeviceDto> CreateDevice(double cpuUtilization, Guid deviceId)
   {
     try
     {
diff --git a/ControlR.Agent/Services/Mac/DeviceGeneratorMac.cs b/ControlR.Agent/Services/Mac/DeviceGeneratorMac.cs
index 2b4d3d6a..482ca270 100644
--- a/ControlR.Agent/Services/Mac/DeviceGeneratorMac.cs
+++ b/ControlR.Agent/Services/Mac/DeviceGeneratorMac.cs
@@ -12,7 +12,7 @@ internal class DeviceDataGeneratorMac(
   private readonly ILogger<DeviceDataGeneratorMac> _logger = logger;
   private readonly IProcessManager _processService = processInvoker;
 
-  public async Task<DeviceDto> CreateDevice(double cpuUtilization, string deviceId)
+  public async Task<DeviceDto> CreateDevice(double cpuUtilization, Guid deviceId)
   {
     try
     {
diff --git a/ControlR.Agent/Services/SettingsProvider.cs b/ControlR.Agent/Services/SettingsProvider.cs
index 954cc1d2..8c29c1d0 100644
--- a/ControlR.Agent/Services/SettingsProvider.cs
+++ b/ControlR.Agent/Services/SettingsProvider.cs
@@ -7,7 +7,7 @@ namespace ControlR.Agent.Services;
 
 internal interface ISettingsProvider
 {
-  string DeviceId { get; }
+  Guid DeviceId { get; }
   bool IsConnectedToPublicServer { get; }
   Uri ServerUri { get; }
   string GetAppSettingsPath();
@@ -23,7 +23,7 @@ internal class SettingsProvider(
   private readonly JsonSerializerOptions _jsonOptions = new() { WriteIndented = true };
   private readonly SemaphoreSlim _updateLock = new(1, 1);
 
-  public string DeviceId => appOptions.CurrentValue.DeviceId;
+  public Guid DeviceId => appOptions.CurrentValue.DeviceId;
 
   public Uri ServerUri =>
     appOptions.CurrentValue.ServerUri ??
diff --git a/ControlR.Agent/Services/Windows/DeviceDataGeneratorWin.cs b/ControlR.Agent/Services/Windows/DeviceDataGeneratorWin.cs
index f96f7ca3..412eb8f8 100644
--- a/ControlR.Agent/Services/Windows/DeviceDataGeneratorWin.cs
+++ b/ControlR.Agent/Services/Windows/DeviceDataGeneratorWin.cs
@@ -14,7 +14,7 @@ internal class DeviceDataGeneratorWin(
 {
   private readonly ILogger<DeviceDataGeneratorWin> _logger = logger;
 
-  public async Task<DeviceDto> CreateDevice(double cpuUtilization, string deviceId)
+  public async Task<DeviceDto> CreateDevice(double cpuUtilization, Guid deviceId)
   {
     try
     {
diff --git a/ControlR.Viewer/Services/DevicesCache.cs b/ControlR.Viewer/Services/DevicesCache.cs
index f327f737..00e78d13 100644
--- a/ControlR.Viewer/Services/DevicesCache.cs
+++ b/ControlR.Viewer/Services/DevicesCache.cs
@@ -18,13 +18,13 @@ public interface IDeviceCache
 
   Task SetAllOffline();
 
-  bool TryGet(string deviceId, [NotNullWhen(true)] out DeviceDto? device);
+  bool TryGet(Guid deviceId, [NotNullWhen(true)] out DeviceDto? device);
 }
 
 internal class DeviceCache(IFileSystem fileSystem, IFileIo fileIo, ILogger<DeviceCache> logger)
   : IDeviceCache
 {
-  private static readonly ConcurrentDictionary<string, DeviceDto> _cache = new();
+  private static readonly ConcurrentDictionary<Guid, DeviceDto> _cache = new();
   private static readonly SemaphoreSlim _fileLock = new(1, 1);
   private readonly string _deviceCachePath = Path.Combine(fileSystem.AppDataDirectory, "DeviceCache.json");
 
@@ -101,7 +101,7 @@ public async Task SetAllOffline()
     await TrySaveCache();
   }
 
-  public bool TryGet(string deviceId, [NotNullWhen(true)] out DeviceDto? device)
+  public bool TryGet(Guid deviceId, [NotNullWhen(true)] out DeviceDto? device)
   {
     return _cache.TryGetValue(deviceId, out device);
   }
diff --git a/ControlR.Viewer/Services/ViewerHubConnection.cs b/ControlR.Viewer/Services/ViewerHubConnection.cs
index 3cf7f76e..7deb21a9 100644
--- a/ControlR.Viewer/Services/ViewerHubConnection.cs
+++ b/ControlR.Viewer/Services/ViewerHubConnection.cs
@@ -23,7 +23,7 @@ public interface IViewerHubConnection : IHubConnectionBase
   Task<Uri?> GetWebsocketBridgeOrigin();
   Task<Result<WindowsSession[]>> GetWindowsSessions(DeviceDto device);
 
-  Task InvokeCtrlAltDel(string deviceId);
+  Task InvokeCtrlAltDel(Guid deviceId);
 
   Task Reconnect(CancellationToken cancellationToken);
 
@@ -103,7 +103,7 @@ await TryInvoke(
   }
 
 
-  public async Task CloseTerminalSession(string deviceId, Guid terminalId)
+  public async Task CloseTerminalSession(Guid deviceId, Guid terminalId)
   {
     await TryInvoke(async () =>
     {
@@ -204,7 +204,7 @@ await Connection.InvokeAsync<WindowsSession[]>(nameof(IViewerHub.GetWindowsSessi
     }
   }
 
-  public async Task InvokeCtrlAltDel(string deviceId)
+  public async Task InvokeCtrlAltDel(Guid deviceId)
   {
     await TryInvoke(async () =>
     {
diff --git a/ControlR.Web.Client/Services/DevicesCache.cs b/ControlR.Web.Client/Services/DevicesCache.cs
index f73c2124..903028eb 100644
--- a/ControlR.Web.Client/Services/DevicesCache.cs
+++ b/ControlR.Web.Client/Services/DevicesCache.cs
@@ -15,12 +15,12 @@ public interface IDeviceCache
 
   Task SetAllOffline();
 
-  bool TryGet(string deviceId, [NotNullWhen(true)] out DeviceDto? device);
+  bool TryGet(Guid deviceId, [NotNullWhen(true)] out DeviceDto? device);
 }
 
 internal class DeviceCache(ILogger<DeviceCache> logger) : IDeviceCache
 {
-  private static readonly ConcurrentDictionary<string, DeviceDto> _cache = new();
+  private static readonly ConcurrentDictionary<Guid, DeviceDto> _cache = new();
   private static readonly SemaphoreSlim _initLock = new(1, 1);
 
   public IEnumerable<DeviceDto> Devices => _cache.Values;
@@ -68,7 +68,7 @@ public Task SetAllOffline()
     return Task.CompletedTask;
   }
 
-  public bool TryGet(string deviceId, [NotNullWhen(true)] out DeviceDto? device)
+  public bool TryGet(Guid deviceId, [NotNullWhen(true)] out DeviceDto? device)
   {
     return _cache.TryGetValue(deviceId, out device);
   }
diff --git a/ControlR.Web.Client/Services/ViewerHubConnection.cs b/ControlR.Web.Client/Services/ViewerHubConnection.cs
index d52a488e..9d3667f6 100644
--- a/ControlR.Web.Client/Services/ViewerHubConnection.cs
+++ b/ControlR.Web.Client/Services/ViewerHubConnection.cs
@@ -11,7 +11,7 @@ namespace ControlR.Web.Client.Services;
 public interface IViewerHubConnection : IHubConnectionBase
 {
   Task ClearAlert();
-  Task CloseTerminalSession(string agentConnectionId, Guid terminalId);
+  Task CloseTerminalSession(Guid deviceId, Guid terminalId);
 
   Task<Result<TerminalSessionRequestResult>> CreateTerminalSession(string agentConnectionId, Guid terminalId);
 
@@ -23,7 +23,7 @@ public interface IViewerHubConnection : IHubConnectionBase
   Task<Uri?> GetWebsocketBridgeOrigin();
   Task<Result<WindowsSession[]>> GetWindowsSessions(DeviceDto device);
 
-  Task InvokeCtrlAltDel(string deviceId);
+  Task InvokeCtrlAltDel(Guid deviceId);
 
   Task Reconnect(CancellationToken cancellationToken);
 
@@ -102,7 +102,7 @@ await TryInvoke(
   }
 
 
-  public async Task CloseTerminalSession(string deviceId, Guid terminalId)
+  public async Task CloseTerminalSession(Guid deviceId, Guid terminalId)
   {
     await TryInvoke(async () =>
     {
@@ -112,8 +112,7 @@ await TryInvoke(async () =>
     });
   }
 
-  public async Task<Result<TerminalSessionRequestResult>> CreateTerminalSession(string agentConnectionId,
-    Guid terminalId)
+  public async Task<Result<TerminalSessionRequestResult>> CreateTerminalSession(string agentConnectionId, Guid terminalId)
   {
     return await TryInvoke(
       async () =>
@@ -197,7 +196,7 @@ public async Task<Result<WindowsSession[]>> GetWindowsSessions(DeviceDto device)
     }
   }
 
-  public async Task InvokeCtrlAltDel(string deviceId)
+  public async Task InvokeCtrlAltDel(Guid deviceId)
   {
     await TryInvoke(async () =>
     {
diff --git a/ControlR.Web.Server/Hubs/AgentHub.cs b/ControlR.Web.Server/Hubs/AgentHub.cs
index b4e7cc1d..cd9597c3 100644
--- a/ControlR.Web.Server/Hubs/AgentHub.cs
+++ b/ControlR.Web.Server/Hubs/AgentHub.cs
@@ -53,7 +53,7 @@ public async Task UpdateDevice(DeviceDto device)
 
       // TODO: Save to DB.
       
-      await Groups.AddToGroupAsync(Context.ConnectionId, device.Id);
+      await Groups.AddToGroupAsync(Context.ConnectionId, HubGroupNames.GetDeviceGroupName(device.Id));
       
       Device = device;
 
diff --git a/ControlR.Web.Server/Hubs/HubGroupNames.cs b/ControlR.Web.Server/Hubs/HubGroupNames.cs
index 848bef30..2ddb79df 100644
--- a/ControlR.Web.Server/Hubs/HubGroupNames.cs
+++ b/ControlR.Web.Server/Hubs/HubGroupNames.cs
@@ -2,5 +2,10 @@
 
 public static class HubGroupNames
 {
-    public const string ServerAdministrators = "server-administrators";
-}
+  public const string ServerAdministrators = "server-administrators";
+
+  public static string GetDeviceGroupName(Guid deviceId)
+  {
+    return $"device-{deviceId}";
+  }
+}
\ No newline at end of file
diff --git a/ControlR.Web.Server/Hubs/ViewerHub.cs b/ControlR.Web.Server/Hubs/ViewerHub.cs
index 3bc55d55..04ad9d2c 100644
--- a/ControlR.Web.Server/Hubs/ViewerHub.cs
+++ b/ControlR.Web.Server/Hubs/ViewerHub.cs
@@ -218,11 +218,11 @@ public async Task<Result> SendAlertBroadcast(AlertBroadcastDto alertDto)
     }
   }
 
-  public async Task SendDtoToAgent(string deviceId, DtoWrapper wrapper)
+  public async Task SendDtoToAgent(Guid deviceId, DtoWrapper wrapper)
   {
     using var scope = logger.BeginMemberScope();
 
-    await agentHub.Clients.Group(deviceId).ReceiveDto(wrapper);
+    await agentHub.Clients.Group(HubGroupNames.GetDeviceGroupName(deviceId)).ReceiveDto(wrapper);
   }
 
   public Task SendDtoToUserGroups(DtoWrapper wrapper)
diff --git a/ControlR.sln.DotSettings b/ControlR.sln.DotSettings
index 7b0cca49..8d242280 100644
--- a/ControlR.sln.DotSettings
+++ b/ControlR.sln.DotSettings
@@ -19,4 +19,5 @@
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ECSharpPlaceEmbeddedOnSameLineMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ECSharpUseContinuousIndentInsideBracesMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateBlankLinesAroundFieldToBlankLinesAroundProperty/@EntryIndexedValue">True</s:Boolean>
-	<s:Boolean x:Key="/Default/UserDictionary/Words/=controlr/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
\ No newline at end of file
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=controlr/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=dtos/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
\ No newline at end of file
diff --git a/Libraries/ControlR.Libraries.Shared/Dtos/DeviceDto.cs b/Libraries/ControlR.Libraries.Shared/Dtos/DeviceDto.cs
index f68e61c4..e72a48d0 100644
--- a/Libraries/ControlR.Libraries.Shared/Dtos/DeviceDto.cs
+++ b/Libraries/ControlR.Libraries.Shared/Dtos/DeviceDto.cs
@@ -35,7 +35,7 @@ public class DeviceDto
 
   [MsgPackKey]
   [Display(Name = "Device Id")]
-  public string Id { get; init; } = string.Empty;
+  public Guid Id { get; init; }
 
   [MsgPackKey]
   [Display(Name = "64-bit")]
diff --git a/Libraries/ControlR.Libraries.Shared/Hubs/IViewerHub.cs b/Libraries/ControlR.Libraries.Shared/Hubs/IViewerHub.cs
index 4e20b2d4..ea07ba78 100644
--- a/Libraries/ControlR.Libraries.Shared/Hubs/IViewerHub.cs
+++ b/Libraries/ControlR.Libraries.Shared/Hubs/IViewerHub.cs
@@ -6,26 +6,27 @@ namespace ControlR.Libraries.Shared.Hubs;
 
 public interface IViewerHub
 {
-    Task<bool> CheckIfServerAdministrator();
+  Task<bool> CheckIfServerAdministrator();
 
-    Task<Result> ClearAlert();
+  Task<Result> ClearAlert();
 
-    Task<Result<TerminalSessionRequestResult>> CreateTerminalSession(string agentConnectionId, TerminalSessionRequest requestDto);
+  Task<Result<TerminalSessionRequestResult>> CreateTerminalSession(string agentConnectionId,
+    TerminalSessionRequest requestDto);
 
-    Task<Result<AgentAppSettings>> GetAgentAppSettings(string agentConnectionId);
+  Task<Result<AgentAppSettings>> GetAgentAppSettings(string agentConnectionId);
 
-    Task<Result<AlertBroadcastDto>> GetCurrentAlert();
+  Task<Result<AlertBroadcastDto>> GetCurrentAlert();
 
-    Task<Result<ServerStatsDto>> GetServerStats();
+  Task<Result<ServerStatsDto>> GetServerStats();
 
-    Task<Uri?> GetWebSocketBridgeOrigin();
-    Task<WindowsSession[]> GetWindowsSessions(string agentConnectionId);
+  Task<Uri?> GetWebSocketBridgeOrigin();
+  Task<WindowsSession[]> GetWindowsSessions(string agentConnectionId);
 
-    Task<Result> RequestStreamingSession(string agentConnectionId, StreamerSessionRequestDto sessionRequestDto);
-    Task<Result> SendAgentAppSettings(string agentConnectionId, AgentAppSettings signedDto);
+  Task<Result> RequestStreamingSession(string agentConnectionId, StreamerSessionRequestDto sessionRequestDto);
+  Task<Result> SendAgentAppSettings(string agentConnectionId, AgentAppSettings signedDto);
 
-    Task<Result> SendAlertBroadcast(AlertBroadcastDto signedDto);
-    Task SendDtoToAgent(string deviceId, DtoWrapper wrapper);
-    Task SendDtoToUserGroups(DtoWrapper wrapper);
-    Task<Result> SendTerminalInput(string agentConnectionId, TerminalInputDto dto);
+  Task<Result> SendAlertBroadcast(AlertBroadcastDto signedDto);
+  Task SendDtoToAgent(Guid deviceId, DtoWrapper wrapper);
+  Task SendDtoToUserGroups(DtoWrapper wrapper);
+  Task<Result> SendTerminalInput(string agentConnectionId, TerminalInputDto dto);
 }
\ No newline at end of file
diff --git a/Libraries/ControlR.Libraries.Shared/Models/AgentAppOptions.cs b/Libraries/ControlR.Libraries.Shared/Models/AgentAppOptions.cs
index f1f27b83..069850a7 100644
--- a/Libraries/ControlR.Libraries.Shared/Models/AgentAppOptions.cs
+++ b/Libraries/ControlR.Libraries.Shared/Models/AgentAppOptions.cs
@@ -9,7 +9,7 @@ public class AgentAppOptions
     public const string SectionKey = "AppOptions";
     
     [MsgPackKey]
-    public string? DeviceId { get; set; }
+    public Guid DeviceId { get; set; }
 
     [MsgPackKey]
     public Uri? ServerUri { get; set; }