HTTP 405 Method Not Allowed to default Blazor Server template – breaks Bing/Google crawl

[vsfeedback]

This issue has been moved from a ticket on Developer Community.

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[severity:It's more difficult to complete my work]
Product/Version
Visual Studio 2022 (17.14.16) – “Blazor Server” template, .NET 9
Problem Description
The ASP.NET Core pipeline generated by the default Blazor Server template rejects HTTP HEAD requests with status 405.
Search-engine crawlers (Bingbot, Googlebot) rely on HEAD to discover page availability; when they receive 405 they report “Crawl error – page cannot be displayed”, preventing site indexing even though the same URL returns 200 for GET.
Repro Steps
File ▸ New ▸ Project ▸ Blazor Server (interactive).
F5 / dotnet run → site listens on e.g. https://localhost:5000/.
In terminal run:
curl -I -X HEAD -A "bingbot" https://localhost:5000/
Response:
HTTP/1.1 405 Method Not Allowed
Server: Kestrel
Allow: GET, POST
Expected Behavior
HEAD should return 200 (same as GET) so crawlers can proceed.
Actual Behavior
405 is returned; Bing/Google report crawl failure.

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Original Comments

Feedback Bot on 10/20/2025, 07:35 AM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

[javiercn]

Thanks for contacting us.

The Blazor server template is no longer shipped since .NET 8.0. Are you talking about Blazor Web with global server interactivity?

[christiannagel]

@javiercn It's the same with Blazor Web with global server interactivity.

HEAD requests can be supported with middleware:

app.Use(async (context, next) =>
{
    if (context.Request.Method == HttpMethods.Head)
    {
        // Temporarily change to GET so Blazor can handle the route
        context.Request.Method = HttpMethods.Get;
        await next();
        // Remove the body for HEAD requests
        context.Response.Body = Stream.Null;
    }
    else
    {
        await next();
    }
});

It would be great if Blazor Server could directly support HEAD requests.

[javiercn]

@christiannagel thanks for the additional details.

Something like this should work for your case.

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapRazorComponents<App>()
   .Add(endpointBuilder =>
   {
       if (endpointBuilder.Metadata.OfType<HttpMethodMetadata>()
           .FirstOrDefault()?.HttpMethods.Contains("GET") == true)
       {
           endpointBuilder.Metadata.Add(
               new HttpMethodMetadata(new[] { "GET", "HEAD" }));
       }
   });

app.Run();

I also believe that MVC/Razor Pages don't support HEAD by default, but I'm willing to be wrong.

[christiannagel]

@javiercn I didn't have 405 in my logs with my website when using MVC/Razor Pages from Bing and google requests. This just started with Blazor.
With Razor Pages, the OnGet method is invoked with a HEAD request - if a OnHead method is not implemented.