--- title: Manage users and groups in SignalR author: bradygaster description: Overview of ASP.NET Core SignalR User and Group management. monikerRange: '>= aspnetcore-2.1' ms.author: wpickett ms.custom: mvc ms.date: 04/04/2024 uid: signalr/groups --- # Manage users and groups in SignalR By [Brennan Conroy](https://github.com/BrennanConroy) SignalR allows messages to be sent to all connections associated with a specific user and to named groups of connections. [View or download sample code](https://github.com/dotnet/AspNetCore.Docs/tree/main/aspnetcore/signalr/groups/sample/) [(how to download)](xref:index#how-to-download-a-sample) ## Users in SignalR A single user in SignalR can have multiple connections to an app. For example, a user could be connected on their desktop as well as their phone. Each device has a separate SignalR connection, but they're all associated with the same user. If a message is sent to the user, all of the connections associated with that user receive the message. The user identifier for a connection can be accessed by the `Context.UserIdentifier` property in the hub. By default, SignalR uses the `ClaimTypes.NameIdentifier` from the `ClaimsPrincipal` associated with the connection as the user identifier. To customize this behavior, see [Use claims to customize identity handling](xref:signalr/authn-and-authz#use-claims-to-customize-identity-handling). Send a message to a specific user by passing the user identifier to the `User` function in a hub method, as shown in the following example: > [!NOTE] > The user identifier is case-sensitive. [!code-csharp[Configure service](groups/sample/Hubs/ChatHub.cs?range=29-32)] ## Groups in SignalR A group is a collection of connections associated with a name. Messages can be sent to all connections in a group. Groups are the recommended way to send to a connection or multiple connections because the groups are managed by the application. A connection can be a member of multiple groups. Groups are ideal for something like a chat application, where each room can be represented as a group. ### Add or remove connections from a group Connections are added to or removed from groups via the `AddToGroupAsync` and `RemoveFromGroupAsync` methods: [!code-csharp[Hub methods](groups/sample/Hubs/ChatHub.cs?range=15-27)] It's safe to add a user to a group multiple times, no exception is thrown in the case that the user already exists in the group. Group membership isn't preserved when a connection reconnects. The connection needs to rejoin the group when it's re-established. It's not possible to count the members of a group, since this information isn't available if the application is scaled to multiple servers. Groups are kept in memory, so they won't persist through a server restart. Consider the Azure SignalR service for scenarios requiring group membership to be persisted. For more information, see [Azure SignalR](/azure/azure-signalr/signalr-overview) To protect access to resources while using groups, use [authentication and authorization](xref:signalr/authn-and-authz) functionality in ASP.NET Core. If a user is added to a group only when the credentials are valid for that group, messages sent to that group will only go to authorized users. However, groups are not a security feature. Authentication claims have features that groups don't, such as expiry and revocation. If a user's permission to access the group is revoked, the app must remove the user from the group explicitly. > [!NOTE] > Group names are case-sensitive. ## Additional resources * * *