Implement Custom Error Pages

A set of tutorials for creating and implementating custom error pages in an Umbraco CMS project.

Umbraco is built on Microsoft's .NET Framework and uses ASP.NET. This provides different options when setting up custom error pages on your website.

Implementing custom error handling can make your site look more on-brand and minimize the impact that errors have on user experience. For example, a custom 404 page with helpful links or a search function can add extra value to your site.

In-code error page handling

In Umbraco, in-code error page handling refers to managing and displaying custom error pages directly through code. This method provides greater flexibility and control over how errors are handled and presented to users, especially within the context of an Umbraco site.

This article contains guides on how to create custom error pages for the most common scenarios:

• 404 Errors ("Page not found")

• 500 Errors ("Internal Server Error")

• Boot Failed Errors

Are you looking for a guide to create a custom maintenance page?

This has been moved to a separate article: Create a custom maintenance page.

404 Errors

This kind of error can occur when something has been removed, when a path has been changed, or when the chosen path is invalid.

This method will use a 404 page created via the backoffice.

Create a 404 page in the backoffice

1. Navigate to the Settings section.

2. Create a new "Document Type with Template".

3. Name the Document Type 404.

4. [Optional] Add properties on the Document Type.

   1. In most cases, the 404 not found page would be static.

5. Fill out the Template with your custom markup.

6. Create another Document Type, but create it without the Template.

7. Call this Document Type Statuscodes.

8. Open the Structure Workspace view.

9. Check the Allow at root option.

10. Add the 404 Document Type as an Allowed child note type.

11. Navigate to the Content section.

12. Create a Statuscodes content item called Statuscodes.

13. Create a 404 content item under the Statuscodes content.

Set a custom 404 page in the configuration

Once that is done, the next step focuses on setting up the appropriate configuration.

1. Take note of the published error page's GUID.

2. Open the appsettings.json file in a code editor.

3. Add the Error404Collection section to Umbraco:CMS:Content, like shown below:

{
    "Umbraco": {
        "CMS": {
            "Content": {
                "Error404Collection": [
                    {
                        "Culture": "default",
                        "ContentKey": "81dbb860-a2e3-49df-9a1c-2e04a8012c03"
                    }
                ]
            }
        }
    }
}

In the above code sample, replace the value for ContentKey with the GUID from step 1.

With this approach, you can set different 404 pages for specific languages/cultures (such as en-us, da-dk, and so on):

"Error404Collection": [
  {
    "Culture": "en-us",
    "ContentKey": "guid-for-english-404"
  },
  {
    "Culture": "da-dk",
    "ContentKey": "guid-for-danish-404"
  }
]

Set a custom 404 page using IContentLastChanceFinder

It is also possible to set up a 404 error page programmatically using IContentLastChanceFinder. To learn more about IContentLastChanceFinder read the Custom Routing article.

Before following this example, follow the Create a 404 page in the backoffice part. The example below will use the Page404 alias of the Document Type to find and display the error page.

1. Create a new .cs file called Error404Page at the root of the project.

2. Add the following code to the newly created class:

Error404Page.cs

using Umbraco.Cms.Core.Composing;
using Umbraco.Cms.Core.Routing;
using Umbraco.Cms.Core.Web;

namespace YourProjectNamespace;

public class Error404Page : IContentLastChanceFinder
{
 private readonly IUmbracoContextAccessor _contextAccessor;

 public Error404Page(IUmbracoContextAccessor contextAccessor)
 {
  _contextAccessor = contextAccessor;
 }

 public Task<bool> TryFindContent(IPublishedRequestBuilder request)
 {
  // In the rare case that an umbracoContext cannot be built from the request,
  // we will not be able to find the page
  if (_contextAccessor.TryGetUmbracoContext(out var umbracoContext) == false)
  {
   return Task.FromResult(false);
  }

  // Find the first notFound page at the root level through the published content cache by its documentTypeAlias
  // You can make this search as complex as you want, you can return different pages based on anything in the original request
  var notFoundPage = umbracoContext.Content?.GetAtRoot().FirstOrDefault(c => c.ContentType.Alias == "Page404");
  if (notFoundPage == null)
  {
   return Task.FromResult(false);
  }

  //Set the content on the request and mark our search as successful
  request.SetPublishedContent(notFoundPage);
  request.SetResponseStatus(404);
  return Task.FromResult(true);
 }
}

// ContentFinders need to be registered into the DI container through a composer
public class Mycomposer : IComposer
{
 public void Compose(IUmbracoBuilder builder)
 {
  builder.SetContentLastChanceFinder<Error404Page>();
 }
}

500 Errors

This section guides you in setting up a custom page for handling internal server errors (500 errors) in your Umbraco site. This setup works when:

• A template throws an error.

• A controller throws an unhandled exception.

• A request hits the application, but something fails during rendering or processing.

Create a 500 error page in the Backoffice

1. Access the Umbraco Backoffice.

2. Navigate to the Settings section.

3. Create a new Document Type with Template called 500.

4. [Optional] Add relevant properties to the Document Types and define the template layout.

5. Fill out the Template with your custom markup.

6. Follow steps 6-9 in the Create a 404 page in the backoffice section.

   • You can skip this if you already have a structure for status code content nodes.

7. Add the 500 Document Type as an Allowed child node type on the Statuscode Document Type.

8. Go to the Content section.

9. Create a Statuscodes content item if one does not exist already.

10. Create a new content node of type 500 under the Statuscodes content node.

Configure programmatic error handling

Now configure the application to display the 500 error page when internal server errors occur.

1. Create a folder called Controllers in the root of your Umbraco project.

2. Create a new file called ErrorController.cs in the Controllers folder.

3. Add the following code to the file:

ErrorController.cs

using Microsoft.AspNetCore.Mvc;

namespace YourProjectNamespace.Controllers;

public class ErrorController : Controller
{
    [Route("Error")]
    public IActionResult Index()
    {
        if (Response.StatusCode == StatusCodes.Status500InternalServerError)
        {
            return Redirect("/statuscodes/500");
        }
        else if (Response.StatusCode != StatusCodes.Status200OK)
        {
            return Redirect("/statuscodes");
        }
        return Redirect("/");
    }
}

Replace YourProjectNamespace with the actual project name. In Visual Studio, you can use Sync Namespaces from the project context menu (in Solution Explorer View).

1. Add the /error/ route to the list of reserved paths in the appSettings.json file:

appSettings.json

"Umbraco": {
"CMS": {
    "Global": {
    "ReservedPaths": "~/app_plugins/,~/install/,~/mini-profiler-resources/,~/umbraco/,~/error/",
    ...
    }
  }
}

1. Update Program.cs to ensure the error route is triggered by unhandled exceptions:

Program.cs

WebApplication app = builder.Build();

if (builder.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}
else
{
    app.UseExceptionHandler("/error");
}

To test this locally, replace app.UseDeveloperExceptionPage(); by app.UseExceptionHandler("/error");. Otherwise, you will get the default error page.

Trigger a 500 error (for testing)

To trigger a 500 error, change a Model.Value property in your template. For example, if your Document Type has a property called testyou would normally render it with:

@Model.Value("test")

To deliberately cause an error, change it to something invalid like:

@Model.ValueTest("test")

This should throw an error, triggering your custom 500 page.

Handling app startup failures

When Umbraco fails to start, you may see a blank screen or receive a 500.30 or 502.5 error. These indicate the web application crashed or failed to initialize.

Why can't the app serve an error page?

During startup, Umbraco relies on the ASP.NET Core pipeline. If the app crashes before this pipeline is fully initialized, it can't handle requests or serve custom error pages. That's why you can't rely on Umbraco or ASP.NET Core routing to show error content at this point as it has already failed. For more information, see the Handle errors in ASP.NET Core documentation.

Instead, the web server itself (IIS, NGINX, Apache, and so on) must serve a static fallback 500 page. This page is independent of the application and helps communicate the issue to users when the site is down.

To handle these types of issues:

• Configure your web server (IIS, NGINX, Apache) to serve a static HTML 500 page when the app fails to respond.

• Use uptime monitoring to catch failed starts.

• Check Umbraco logs in App_Data/Logs for startup errors.

Boot Failed Errors

Sometimes you might experience issues with booting up your Umbraco project. This could be a brand new project, or it could be an existing project after an upgrade.

You will be presented with a generic error page when there is an error during boot.

Boot Failed

You can replace the default BootFailed page with a custom static BootFailed.html. Follow the steps below to set it up:

1. Open your project files.

2. Navigate to wwwroot/config/errors

   1. If this folder does not exist already, create it.

3. Add a new file called BootFailed.html.

4. Add your custom markup to the file.

The BootFailed.html page will only be shown if debugging is disabled in the appsettings.json file. Debugging is handled using the Debug key under Umbraco:CMS:Hosting:

appSettings.json

{
    "Umbraco": {
        "CMS": {
            "Hosting": {
                "Debug": false
            }
        }
    }
}

The full error can always be found in the log file.

Are the error pages not working?

If you set up everything correctly and the error pages are not showing correctly, make sure that you are not using

• Custom ContentFinders in your solution,
• Any packages that allow you to customize redirects, or

• Rewrite rules that might interfere with custom error handling.

If your code or any packages configure a custom IContentLastChanceFinder, the settings in appSettings.json will not be used.

Handling errors in ASP.NET Core

For common approaches to handling errors in ASP.NET Core web apps, see the Handle errors in ASP.NET Core article in the Microsoft Documentation.