title	author	description	monikerRange	ms.author	ms.custom	ms.date	uid
ASP.NET Core Blazor authentication and authorization	guardrex	Learn about Blazor authentication and authorization scenarios.	>= aspnetcore-3.1	riande	mvc	11/14/2023	blazor/security/index

ASP.NET Core Blazor authentication and authorization

[!INCLUDE]

This article describes ASP.NET Core's support for the configuration and management of security in Blazor apps.

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Security scenarios differ between server-side and client-side Blazor apps. Because a server-side app runs on the server, authorization checks are able to determine:

The UI options presented to a user (for example, which menu entries are available to a user).
Access rules for areas of the app and components.

For a client-side app, authorization is only used to determine which UI options to show. Since client-side checks can be modified or bypassed by a user, a client-side app can't enforce authorization access rules.

:::moniker range=">= aspnetcore-8.0"

Razor Pages authorization conventions don't apply to routable Razor components. If a non-routable Razor component is embedded in a page of a Razor Pages app, the page's authorization conventions indirectly affect the Razor component along with the rest of the page's content.

:::moniker-end

:::moniker range="< aspnetcore-8.0"

Razor Pages authorization conventions don't apply to routable Razor components. If a non-routable Razor component is embedded in a page of a Razor Pages app, the page's authorization conventions indirectly affect the Razor component along with the rest of the page's content.

:::moniker-end

:::moniker range="< aspnetcore-8.0"

ASP.NET Core Identity is designed to work in the context of HTTP request and response communication, which generally isn't the Blazor app client-server communication model. ASP.NET Core apps that use ASP.NET Core Identity for user management should use Razor Pages instead of Razor components for Identity-related UI, such as user registration, login, logout, and other user management tasks. Building Razor components that directly handle Identity tasks is possible for several scenarios but isn't recommended or supported by Microsoft.

ASP.NET Core abstractions, such as xref:Microsoft.AspNetCore.Identity.SignInManager%601 and xref:Microsoft.AspNetCore.Identity.UserManager%601, aren't supported in Razor components. For more information on using ASP.NET Core Identity with Blazor, see Scaffold ASP.NET Core Identity into a server-side Blazor app.

:::moniker-end

Note

The code examples in this article adopt nullable reference types (NRTs) and .NET compiler null-state static analysis, which are supported in ASP.NET Core 6.0 or later. When targeting ASP.NET Core 5.0 or earlier, remove the null type designation (?) from examples in this article.

:::moniker range=">= aspnetcore-8.0"

Antiforgery support

Blazor adds Antiforgery Middleware and requires endpoint antiforgery protection by default.

The xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryToken component renders an antiforgery token as a hidden field, and this component is automatically added to form (xref:Microsoft.AspNetCore.Components.Forms.EditForm) instances. For more information, see xref:blazor/forms/index#antiforgery-support.

The xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryStateProvider service provides access to an antiforgery token associated with the current session. Inject the service and call its xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryStateProvider.GetAntiforgeryToken method to obtain the current xref:Microsoft.AspNetCore.Components.Forms.AntiforgeryRequestToken. For more information, see xref:blazor/call-web-api#antiforgery-support.

Blazor stores request tokens in component state, which guarantees that antiforgery tokens are available to interactive components, even when they don't have access to the request.

:::moniker-end

Authentication

Blazor uses the existing ASP.NET Core authentication mechanisms to establish the user's identity. The exact mechanism depends on how the Blazor app is hosted, server-side or client-side.

Server-side Blazor authentication

Server-side Blazor operates over a SignalR connection with the client. Authentication in SignalR-based apps is handled when the connection is established. Authentication can be based on a cookie or some other bearer token, but authentication is managed via the SignalR hub and entirely within the circuit.

The built-in xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider service obtains authentication state data from ASP.NET Core's xref:Microsoft.AspNetCore.Http.HttpContext.User%2A?displayProperty=nameWithType. This is how authentication state integrates with existing ASP.NET Core authentication mechanisms.

`IHttpContextAccessor`/`HttpContext` in Razor components

[!INCLUDE]

Shared state

[!INCLUDE]

Client-side Blazor authentication

In client-side Blazor apps, authentication checks can be bypassed because all client-side code can be modified by users. The same is true for all client-side app technologies, including JavaScript SPA frameworks and native apps for any operating system.

Add the following:

A package reference for the Microsoft.AspNetCore.Components.Authorization NuGet package.

[!INCLUDE]
The xref:Microsoft.AspNetCore.Components.Authorization?displayProperty=fullName namespace to the app's _Imports.razor file.

To handle authentication, use of the built-in or custom xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider service is covered in the following sections.

For more information, see xref:blazor/security/webassembly/index.

`AuthenticationStateProvider` service

:::moniker range=">= aspnetcore-8.0"

xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider is the underlying service used by the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView component and cascading authentication services to obtain the authentication state for a user.

:::moniker-end

:::moniker range="< aspnetcore-8.0"

xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider is the underlying service used by the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView component and xref:Microsoft.AspNetCore.Components.Authorization.CascadingAuthenticationState component to obtain the authentication state for a user.

:::moniker-end

You don't typically use xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider directly. Use the AuthorizeView component or Task<AuthenticationState> approaches described later in this article. The main drawback to using xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider directly is that the component isn't notified automatically if the underlying authentication state data changes.

Note

To implement a custom xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider, see xref:blazor/security/server/index#implement-a-custom-authenticationstateprovider.

The xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider service can provide the current user's xref:System.Security.Claims.ClaimsPrincipal data, as shown in the following example.

ClaimsPrincipalData.razor:

:::moniker range=">= aspnetcore-8.0"

@page "/claims-principle-data"
@rendermode InteractiveServer
@using System.Security.Claims
@inject AuthenticationStateProvider AuthenticationStateProvider

<h1>ClaimsPrincipal Data</h1>

<button @onclick="GetClaimsPrincipalData">Get ClaimsPrincipal Data</button>

<p>@authMessage</p>

@if (claims.Count() > 0)
{
    <ul>
        @foreach (var claim in claims)
        {
            <li>@claim.Type: @claim.Value</li>
        }
    </ul>
}

<p>@surname</p>

@code {
    private string? authMessage;
    private string? surname;
    private IEnumerable<Claim> claims = Enumerable.Empty<Claim>();

    private async Task GetClaimsPrincipalData()
    {
        var authState = await AuthenticationStateProvider
            .GetAuthenticationStateAsync();
        var user = authState.User;

        if (user.Identity is not null && user.Identity.IsAuthenticated)
        {
            authMessage = $"{user.Identity.Name} is authenticated.";
            claims = user.Claims;
            surname = user.FindFirst(c => c.Type == ClaimTypes.Surname)?.Value;
        }
        else
        {
            authMessage = "The user is NOT authenticated.";
        }
    }
}

:::moniker-end

:::moniker range="< aspnetcore-8.0"

@page "/claims-principle-data"
@using System.Security.Claims
@inject AuthenticationStateProvider AuthenticationStateProvider

<h1>ClaimsPrincipal Data</h1>

<button @onclick="GetClaimsPrincipalData">Get ClaimsPrincipal Data</button>

<p>@authMessage</p>

@if (claims.Count() > 0)
{
    <ul>
        @foreach (var claim in claims)
        {
            <li>@claim.Type: @claim.Value</li>
        }
    </ul>
}

<p>@surname</p>

@code {
    private string? authMessage;
    private string? surname;
    private IEnumerable<Claim> claims = Enumerable.Empty<Claim>();

    private async Task GetClaimsPrincipalData()
    {
        var authState = await AuthenticationStateProvider
            .GetAuthenticationStateAsync();
        var user = authState.User;

        if (user.Identity is not null && user.Identity.IsAuthenticated)
        {
            authMessage = $"{user.Identity.Name} is authenticated.";
            claims = user.Claims;
            surname = user.FindFirst(c => c.Type == ClaimTypes.Surname)?.Value;
        }
        else
        {
            authMessage = "The user is NOT authenticated.";
        }
    }
}

:::moniker-end

If user.Identity.IsAuthenticated is true and because the user is a xref:System.Security.Claims.ClaimsPrincipal, claims can be enumerated and membership in roles evaluated.

For more information on dependency injection (DI) and services, see xref:blazor/fundamentals/dependency-injection and xref:fundamentals/dependency-injection. For information on how to implement a custom xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider in server-side Blazor apps, see xref:blazor/security/server/index#implement-a-custom-authenticationstateprovider.

Expose the authentication state as a cascading parameter

If authentication state data is required for procedural logic, such as when performing an action triggered by the user, obtain the authentication state data by defining a cascading parameter of type Task<xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState>, as the following example demonstrates.

CascadeAuthState.razor:

:::moniker range=">= aspnetcore-8.0"

@page "/cascade-auth-state"
@rendermode InteractiveServer

<h1>Cascade Auth State</h1>

<p>@authMessage</p>

@code {
    private string authMessage = "The user is NOT authenticated.";

    [CascadingParameter]
    private Task<AuthenticationState>? authenticationState { get; set; }

    protected override async Task OnInitializedAsync()
    {
        if (authenticationState is not null)
        {
            var authState = await authenticationState;
            var user = authState?.User;

            if (user?.Identity is not null && user.Identity.IsAuthenticated)
            {
                authMessage = $"{user.Identity.Name} is authenticated.";
            }
        }
    }
}

:::moniker-end

:::moniker range="< aspnetcore-8.0"

@page "/cascade-auth-state"

<h1>Cascade Auth State</h1>

<p>@authMessage</p>

@code {
    private string authMessage = "The user is NOT authenticated.";

    [CascadingParameter]
    private Task<AuthenticationState>? authenticationState { get; set; }

    protected override async Task OnInitializedAsync()
    {
        if (authenticationState is not null)
        {
            var authState = await authenticationState;
            var user = authState?.User;

            if (user?.Identity is not null && user.Identity.IsAuthenticated)
            {
                authMessage = $"{user.Identity.Name} is authenticated.";
            }
        }
    }
}

:::moniker-end

If user.Identity.IsAuthenticated is true, claims can be enumerated and membership in roles evaluated.

:::moniker range=">= aspnetcore-8.0"

Set up the Task<xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState> cascading parameter using the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView and cascading authentication state services.

When you create a Blazor app from one of the Blazor project templates with authentication enabled, the app includes the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView and the call to xref:Microsoft.Extensions.DependencyInjection.CascadingAuthenticationStateServiceCollectionExtensions.AddCascadingAuthenticationState%2A shown in the following example. A client-side Blazor app includes the required service registrations as well. Additional information is presented in the Customize unauthorized content with the Router component section.

<Router ...>
    <Found ...>
        <AuthorizeRouteView RouteData="@routeData" 
            DefaultLayout="@typeof(Layout.MainLayout)" />
        ...
    </Found>
</Router>

In the Program file, register cascading authentication state services:

builder.Services.AddCascadingAuthenticationState();

:::moniker-end

:::moniker range="< aspnetcore-8.0"

Set up the Task<xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState> cascading parameter using the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView and xref:Microsoft.AspNetCore.Components.Authorization.CascadingAuthenticationState components.

When you create a Blazor app from one of the Blazor project templates with authentication enabled, the app includes the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView and xref:Microsoft.AspNetCore.Components.Authorization.CascadingAuthenticationState components shown in the following example. A client-side Blazor app includes the required service registrations as well. Additional information is presented in the Customize unauthorized content with the Router component section.

<CascadingAuthenticationState>
    <Router ...>
        <Found ...>
            <AuthorizeRouteView RouteData="@routeData" 
                DefaultLayout="@typeof(MainLayout)" />
            ...
        </Found>
    </Router>
</CascadingAuthenticationState>

:::moniker-end

:::moniker range="= aspnetcore-5.0"

[!INCLUDE]

:::moniker-end

In a client-side Blazor app, add services for options and authorization to the Program file:

builder.Services.AddOptions();
builder.Services.AddAuthorizationCore();

In a server-side Blazor app, services for options and authorization are already present, so no further steps are required.

Authorization

After a user is authenticated, authorization rules are applied to control what the user can do.

Access is typically granted or denied based on whether:

A user is authenticated (signed in).
A user is in a role.
A user has a claim.
A policy is satisfied.

Each of these concepts is the same as in an ASP.NET Core MVC or Razor Pages app. For more information on ASP.NET Core security, see the articles under ASP.NET Core Security and Identity.

`AuthorizeView` component

The xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView component selectively displays UI content depending on whether the user is authorized. This approach is useful when you only need to display data for the user and don't need to use the user's identity in procedural logic.

The component exposes a context variable of type xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState (@context in Razor syntax), which you can use to access information about the signed-in user:

<AuthorizeView>
    <p>Hello, @context.User.Identity?.Name!</p>
</AuthorizeView>

You can also supply different content for display if the user isn't authorized:

<AuthorizeView>
    <Authorized>
        <p>Hello, @context.User.Identity?.Name!</p>
        <p><button @onclick="SecureMethod">Authorized Only Button</button></p>
    </Authorized>
    <NotAuthorized>
        <p>You're not authorized.</p>
    </NotAuthorized>
</AuthorizeView>

@code {
    private void SecureMethod() { ... }
}

A default event handler for an authorized element, such as the SecureMethod method for the <button> element in the preceding example, can only be invoked by an authorized user.

Warning

Client-side markup and methods associated with an xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView are only protected from view and execution in the rendered UI in client-side Blazor apps. In order to protect authorized content and secure methods in client-side Blazor, the content is usually supplied by a secure, authorized web API call to a server API and never stored in the app. For more information, see xref:blazor/call-web-api and xref:blazor/security/webassembly/additional-scenarios.

The content of <Authorized> and <NotAuthorized> tags can include arbitrary items, such as other interactive components.

Authorization conditions, such as roles or policies that control UI options or access, are covered in the Authorization section.

If authorization conditions aren't specified, xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView uses a default policy:

Authenticated (signed-in) users are authorized.
Unauthenticated (signed-out) users are unauthorized.

The xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView component can be used in the NavMenu component (Shared/NavMenu.razor) to display a NavLink component (xref:Microsoft.AspNetCore.Components.Routing.NavLink), but note that this approach only removes the list item from the rendered output. It doesn't prevent the user from navigating to the component. Implement authorization separately in the destination component.

Role-based and policy-based authorization

The xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView component supports role-based or policy-based authorization.

For role-based authorization, use the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView.Roles parameter. In the following example, the user must have a role claim for either the Admin or Superuser roles:

<AuthorizeView Roles="Admin, Superuser">
    <p>You have an 'Admin' or 'Superuser' role claim.</p>
</AuthorizeView>

To require a user have both Admin and Superuser role claims, nest xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView components:

<AuthorizeView Roles="Admin">
    <p>User: @context.User</p>
    <p>You have the 'Admin' role claim.</p>
    <AuthorizeView Roles="Superuser" Context="innerContext">
        <p>User: @innerContext.User</p>
        <p>You have both 'Admin' and 'Superuser' role claims.</p>
    </AuthorizeView>
</AuthorizeView>

The preceding code establishes a Context for the inner xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView component to prevent an xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState context collision. The xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState context is accessed in the outer xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView with the standard approach for accessing the context (@context.User). The context is accessed in the inner xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView with the named innerContext context (@innerContext.User).

For more information, including configuration guidance, see xref:security/authorization/roles.

For policy-based authorization, use the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView.Policy parameter with a single policy:

<AuthorizeView Policy="Over21">
    <p>You satisfy the 'Over21' policy.</p>
</AuthorizeView>

To handle the case where the user should satisfy one of several policies, create a policy that confirms that the user satisfies other policies.

To handle the case where the user must satisfy several policies simultaneously, take either of the following approaches:

Create a policy for xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView that confirms that the user satisfies several other policies.

Nest the policies in multiple xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView components:

<AuthorizeView Policy="Over21">
    <AuthorizeView Policy="LivesInCalifornia">
        <p>You satisfy the 'Over21' and 'LivesInCalifornia' policies.</p>
    </AuthorizeView>
</AuthorizeView>

Claims-based authorization is a special case of policy-based authorization. For example, you can define a policy that requires users to have a certain claim. For more information, see xref:security/authorization/policies.

If neither xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView.Roles nor xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView.Policy is specified, xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView uses the default policy:

Authenticated (signed-in) users are authorized.
Unauthenticated (signed-out) users are unauthorized.

Because .NET string comparisons are case-sensitive by default, matching role and policy names is also case-sensitive. For example, Admin (uppercase A) is not treated as the same role as admin (lowercase a).

Pascal case is typically used for role and policy names (for example, BillingAdministrator), but the use of Pascal case isn't a strict requirement. Different casing schemes, such as camel case, kebab case, and snake case, are permitted. Using spaces in role and policy names is unusual but permitted by the framework. For example, billing administrator is an unusual role or policy name format in .NET apps, but it's a valid role or policy name.

Content displayed during asynchronous authentication

Blazor allows for authentication state to be determined asynchronously. The primary scenario for this approach is in client-side Blazor apps that make a request to an external endpoint for authentication.

While authentication is in progress, xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView displays no content by default. To display content while authentication occurs, use the <Authorizing> tag:

<AuthorizeView>
    <Authorized>
        <p>Hello, @context.User.Identity?.Name!</p>
    </Authorized>
    <Authorizing>
        <p>You can only see this content while authentication is in progress.</p>
    </Authorizing>
</AuthorizeView>

This approach isn't normally applicable to server-side Blazor apps. Server-side Blazor apps know the authentication state as soon as the state is established. xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeViewCore.Authorizing content can be provided in an app's xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView component, but the content is never displayed.

`[Authorize]` attribute

The [Authorize] attribute is available in Razor components:

@page "/"
@attribute [Authorize]

You can only see this if you're signed in.

Important

Only use [Authorize] on @page components reached via the Blazor router. Authorization is only performed as an aspect of routing and not for child components rendered within a page. To authorize the display of specific parts within a page, use xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeView instead.

The [Authorize] attribute also supports role-based or policy-based authorization. For role-based authorization, use the xref:Microsoft.AspNetCore.Authorization.AuthorizeAttribute.Roles parameter:

@page "/"
@attribute [Authorize(Roles = "Admin, Superuser")]

<p>You can only see this if you're in the 'Admin' or 'Superuser' role.</p>

For policy-based authorization, use the xref:Microsoft.AspNetCore.Authorization.AuthorizeAttribute.Policy parameter:

@page "/"
@attribute [Authorize(Policy = "Over21")]

<p>You can only see this if you satisfy the 'Over21' policy.</p>

If neither xref:Microsoft.AspNetCore.Authorization.AuthorizeAttribute.Roles nor xref:Microsoft.AspNetCore.Authorization.AuthorizeAttribute.Policy is specified, [Authorize] uses the default policy:

Authenticated (signed-in) users are authorized.
Unauthenticated (signed-out) users are unauthorized.

When the user isn't authorized and if the app doesn't customize unauthorized content with the Router component, the framework automatically displays the following fallback message:

Not authorized.

:::moniker range=">= aspnetcore-5.0"

Resource authorization

To authorize users for resources, pass the request's route data to the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView.Resource parameter of xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView.

In the xref:Microsoft.AspNetCore.Components.Routing.Router.Found?displayProperty=nameWithType content for a requested route:

<AuthorizeRouteView Resource="@routeData" RouteData="@routeData" 
    DefaultLayout="@typeof(MainLayout)" />

For more information on how authorization state data is passed and used in procedural logic, see the Expose the authentication state as a cascading parameter section.

When the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView receives the route data for the resource, authorization policies have access to xref:Microsoft.AspNetCore.Components.RouteData.PageType?displayProperty=nameWithType and xref:Microsoft.AspNetCore.Components.RouteData.RouteValues?displayProperty=nameWithType that permit custom logic to make authorization decisions.

In the following example, an EditUser policy is created in xref:Microsoft.AspNetCore.Authorization.AuthorizationOptions for the app's authorization service configuration (xref:Microsoft.Extensions.DependencyInjection.AuthorizationServiceCollectionExtensions.AddAuthorizationCore%2A) with the following logic:

Determine if a route value exists with a key of id. If the key exists, the route value is stored in value.
In a variable named id, store value as a string or set an empty string value (string.Empty).
If id isn't an empty string, assert that the policy is satisfied (return true) if the string's value starts with EMP. Otherwise, assert that the policy fails (return false).

In the Program file:

Add namespaces for xref:Microsoft.AspNetCore.Components?displayProperty=fullName and xref:System.Linq?displayProperty=fullName:
```
using Microsoft.AspNetCore.Components;
using System.Linq;
```

Add the policy:

options.AddPolicy("EditUser", policy =>
    policy.RequireAssertion(context =>
    {
        if (context.Resource is RouteData rd)
        {
            var routeValue = rd.RouteValues.TryGetValue("id", out var value);
            var id = Convert.ToString(value, 
                System.Globalization.CultureInfo.InvariantCulture) ?? string.Empty;

            if (!string.IsNullOrEmpty(id))
            {
                return id.StartsWith("EMP", StringComparison.InvariantCulture);
            }
        }

        return false;
    })
);

The preceding example is an oversimplified authorization policy, merely used to demonstrate the concept with a working example. For more information on creating and configuring authorization policies, see xref:security/authorization/policies.

In the following EditUser component, the resource at /users/{id}/edit has a route parameter for the user's identifier ({id}). The component uses the preceding EditUser authorization policy to determine if the route value for id starts with EMP. If id starts with EMP, the policy succeeds and access to the component is authorized. If id starts with a value other than EMP or if id is an empty string, the policy fails, and the component doesn't load.

EditUser.razor:

:::moniker-end

:::moniker range=">= aspnetcore-8.0"

@page "/users/{id}/edit"
@rendermode InteractiveServer
@using Microsoft.AspNetCore.Authorization
@attribute [Authorize(Policy = "EditUser")]

<h1>Edit User</h1>

<p>The "EditUser" policy is satisfied! <code>Id</code> starts with 'EMP'.</p>

@code {
    [Parameter]
    public string? Id { get; set; }
}

:::moniker-end

:::moniker range=">= aspnetcore-5.0 < aspnetcore-8.0"

@page "/users/{id}/edit"
@using Microsoft.AspNetCore.Authorization
@attribute [Authorize(Policy = "EditUser")]

<h1>Edit User</h1>

<p>The "EditUser" policy is satisfied! <code>Id</code> starts with 'EMP'.</p>

@code {
    [Parameter]
    public string? Id { get; set; }
}

:::moniker-end

Customize unauthorized content with the Router component

The xref:Microsoft.AspNetCore.Components.Routing.Router component, in conjunction with the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView component, allows the app to specify custom content if:

The user fails an [Authorize] condition applied to the component. The markup of the <NotAuthorized> element is displayed. The [Authorize] attribute is covered in the [Authorize] attribute section.
Asynchronous authorization is in progress, which usually means that the process of authenticating the user is in progress. The markup of the <Authorizing> element is displayed.

:::moniker range=">= aspnetcore-8.0"

<Router ...>
    <Found ...>
        <AuthorizeRouteView ...>
            <NotAuthorized>
                ...
            </NotAuthorized>
            <Authorizing>
                ...
            </Authorizing>
        </AuthorizeRouteView>
    </Found>
</Router>

The content of <NotAuthorized> and <Authorizing> tags can include arbitrary items, such as other interactive components.

Note

The preceding requires cascading authentication state services registration in the app's Program file:

builder.Services.AddCascadingAuthenticationState();

:::moniker-end

:::moniker range="< aspnetcore-8.0"

<CascadingAuthenticationState>
    <Router ...>
        <Found ...>
            <AuthorizeRouteView ...>
                <NotAuthorized>
                    ...
                </NotAuthorized>
                <Authorizing>
                    ...
                </Authorizing>
            </AuthorizeRouteView>
        </Found>
    </Router>
</CascadingAuthenticationState>

The content of <NotFound>, <NotAuthorized>, and <Authorizing> tags can include arbitrary items, such as other interactive components.

:::moniker-end

If the <NotAuthorized> tag isn't specified, the xref:Microsoft.AspNetCore.Components.Authorization.AuthorizeRouteView uses the following fallback message:

Not authorized.

An app created from the Blazor WebAssembly project template with authentication enabled includes a RedirectToLogin component, which is positioned in the <NotAuthorized> content of the xref:Microsoft.AspNetCore.Components.Routing.Router component. When a user isn't authenticated (context.User.Identity?.IsAuthenticated != true), the RedirectToLogin component redirects the browser to the authentication/login endpoint for authentication. The user is returned to the requested URL after authenticating with the identity provider.

Procedural logic

If the app is required to check authorization rules as part of procedural logic, use a cascaded parameter of type Task<xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState> to obtain the user's xref:System.Security.Claims.ClaimsPrincipal. Task<xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState> can be combined with other services, such as IAuthorizationService, to evaluate policies.

In the following example:

The user.Identity.IsAuthenticated executes code for authenticated (signed-in) users.
The user.IsInRole("admin") executes code for users in the 'Admin' role.
The (await AuthorizationService.AuthorizeAsync(user, "content-editor")).Succeeded executes code for users satisfying the 'content-editor' policy.

A server-side Blazor app includes the appropriate namespaces by default when created from the project template. In a client-side Blazor app, confirm the presence of the xref:Microsoft.AspNetCore.Authorization and xref:Microsoft.AspNetCore.Components.Authorization namespaces either in the component or in the app's _Imports.razor file:

@using Microsoft.AspNetCore.Authorization
@using Microsoft.AspNetCore.Components.Authorization

ProceduralLogic.razor:

:::moniker range=">= aspnetcore-8.0"

@page "/procedural-logic"
@rendermode InteractiveServer
@inject IAuthorizationService AuthorizationService

<h1>Procedural Logic Example</h1>

<button @onclick="@DoSomething">Do something important</button>

@code {
    [CascadingParameter]
    private Task<AuthenticationState>? authenticationState { get; set; }

    private async Task DoSomething()
    {
        if (authenticationState is not null)
        {
            var authState = await authenticationState;
            var user = authState?.User;

            if (user is not null)
            {
                if (user.Identity is not null && user.Identity.IsAuthenticated)
                {
                    // ...
                }

                if (user.IsInRole("Admin"))
                {
                    // ...
                }

                if ((await AuthorizationService.AuthorizeAsync(user, "content-editor"))
                    .Succeeded)
                {
                    // ...
                }
            }
        }
    }
}

:::moniker-end

:::moniker range="< aspnetcore-8.0"

@page "/procedural-logic"
@inject IAuthorizationService AuthorizationService

<h1>Procedural Logic Example</h1>

<button @onclick="@DoSomething">Do something important</button>

@code {
    [CascadingParameter]
    private Task<AuthenticationState>? authenticationState { get; set; }

    private async Task DoSomething()
    {
        if (authenticationState is not null)
        {
            var authState = await authenticationState;
            var user = authState?.User;

            if (user is not null)
            {
                if (user.Identity is not null && user.Identity.IsAuthenticated)
                {
                    // ...
                }

                if (user.IsInRole("Admin"))
                {
                    // ...
                }

                if ((await AuthorizationService.AuthorizeAsync(user, "content-editor"))
                    .Succeeded)
                {
                    // ...
                }
            }
        }
    }
}

:::moniker-end

Troubleshoot errors

Common errors:

Authorization requires a cascading parameter of type Task<AuthenticationState>. Consider using CascadingAuthenticationState to supply this.
null value is received for authenticationStateTask

It's likely that the project wasn't created using a server-side Blazor template with authentication enabled.

In .NET 7 or earlier, wrap a <CascadingAuthenticationState> around some part of the UI tree, for example around the Blazor router:

<CascadingAuthenticationState>
    <Router ...>
        ...
    </Router>
</CascadingAuthenticationState>

In .NET 8 or later, don't use the xref:Microsoft.AspNetCore.Components.Authorization.CascadingAuthenticationState component:

- <CascadingAuthenticationState>
      <Router ...>
          ...
      </Router>
- </CascadingAuthenticationState>

Instead, add cascading authentication state services to the service collection in the Program file:

builder.Services.AddCascadingAuthenticationState();

The xref:Microsoft.AspNetCore.Components.Authorization.CascadingAuthenticationState component (.NET 7 or earlier) or services provided by xref:Microsoft.Extensions.DependencyInjection.CascadingAuthenticationStateServiceCollectionExtensions.AddCascadingAuthenticationState%2A (.NET 8 or later) supplies the Task<xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationState> cascading parameter, which in turn it receives from the underlying xref:Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider dependency injection service.

Additional resources

:::moniker range=">= aspnetcore-6.0"

Microsoft identity platform documentation
xref:security/index
xref:security/authentication/windowsauth
Build a custom version of the Authentication.MSAL JavaScript library
Awesome Blazor: Authentication community sample links
xref:blazor/hybrid/security/index

:::moniker-end

:::moniker range="< aspnetcore-6.0"

Microsoft identity platform documentation
xref:security/index
xref:security/authentication/windowsauth
Build a custom version of the Authentication.MSAL JavaScript library
Awesome Blazor: Authentication community sample links

:::moniker-end

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index.md

index.md

ASP.NET Core Blazor authentication and authorization

Antiforgery support

Authentication

Server-side Blazor authentication

`IHttpContextAccessor`/`HttpContext` in Razor components

Shared state

Client-side Blazor authentication

`AuthenticationStateProvider` service

Expose the authentication state as a cascading parameter

Authorization

`AuthorizeView` component

Role-based and policy-based authorization

Content displayed during asynchronous authentication

`[Authorize]` attribute

Resource authorization

Customize unauthorized content with the Router component

Procedural logic

Troubleshoot errors

Additional resources

Files

index.md

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index.md

File metadata and controls

ASP.NET Core Blazor authentication and authorization

Antiforgery support

Authentication

Server-side Blazor authentication

IHttpContextAccessor/HttpContext in Razor components

Shared state

Client-side Blazor authentication

AuthenticationStateProvider service

Expose the authentication state as a cascading parameter

Authorization

AuthorizeView component

Role-based and policy-based authorization

Content displayed during asynchronous authentication

[Authorize] attribute

Resource authorization

Customize unauthorized content with the Router component

Procedural logic

Troubleshoot errors

Additional resources

`IHttpContextAccessor`/`HttpContext` in Razor components

`AuthenticationStateProvider` service

`AuthorizeView` component

`[Authorize]` attribute