HttpCat.AspNetCore 1.0.0

.NET 8.0 This package targets .NET 8.0. The package is compatible with this framework or higher.
There is a newer version of this package available.
See the version list below for details. 
dotnet add package HttpCat.AspNetCore --version 1.0.0
                    


                    

                
NuGet\Install-Package HttpCat.AspNetCore -Version 1.0.0
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package. 
<PackageReference Include="HttpCat.AspNetCore" Version="1.0.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package. 
<PackageVersion Include="HttpCat.AspNetCore" Version="1.0.0" />
                    


                            Directory.Packages.props
                        

                    

                
<PackageReference Include="HttpCat.AspNetCore" />
                    


                            Project file
For projects that support Central Package Management (CPM), copy this XML node into the solution Directory.Packages.props file to version the package. 
paket add HttpCat.AspNetCore --version 1.0.0
                    


                    

                
#r "nuget: HttpCat.AspNetCore, 1.0.0"
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package. 
#:package HttpCat.AspNetCore@1.0.0
#:package directive can be used in C# file-based apps starting in .NET 10 preview 4. Copy this into a .cs file before any lines of code to reference the package. 
#addin nuget:?package=HttpCat.AspNetCore&version=1.0.0
                    


                            Install as a Cake Addin
                        

                    

                
#tool nuget:?package=HttpCat.AspNetCore&version=1.0.0
                    


                            Install as a Cake Tool

HttpCat.AspNetCore

ASP.NET Core middleware that swaps error responses for embedded HTTP cat images without changing the status code or breaking API contracts.

Why

  • Ships with embedded JPEGs for common HTTP status codes
  • Response buffering keeps headers safe and untouched when not intercepting
  • Opt-in hooks via header or query for debugging scenarios
  • Works with browsers by default (requires text/html Accept unless opt-in is used)

Install

dotnet add package HttpCat.AspNetCore

Use

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddHttpCats();

var app = builder.Build();
app.UseHttpCats();

app.MapGet("/notfound", () => Results.NotFound());
app.MapGet("/server-error", () => Results.StatusCode(500));

app.Run();

Options

builder.Services.AddHttpCats(options =>
{
    options.OnlyOnEmptyBody = true;                 // skip when a body already exists
    options.OnlyForHtmlAcceptHeader = true;          // require Accept: text/html
    options.AllowJsonResponses = false;              // ignore JSON unless enabled
    options.StatusCodePredicate = code => code >= 400 && code <= 599;
    options.OptInHeaderName = "X-HttpCat";           // set "true" or "1" to force
    options.OptInQueryKey = "httpcat";               // ?httpcat=true to force
});

The opt-in header/query bypasses the HTML and JSON checks, which is useful when testing APIs with non-browser clients.

Sample

Run the minimal API in samples/MinimalApiSample:

cd samples/MinimalApiSample
dotnet run

Try /notfound or /server-error from a browser to see cats. /json-error stays JSON by default.

Development

  • Build: dotnet build
  • Tests: dotnet test

Targets net10.0 and net8.0. Licensed under MIT.

Product Compatible and additional computed target framework versions.
.NET net8.0 is compatible.  net8.0-android was computed.  net8.0-browser was computed.  net8.0-ios was computed.  net8.0-maccatalyst was computed.  net8.0-macos was computed.  net8.0-tvos was computed.  net8.0-windows was computed.  net9.0 was computed.  net9.0-android was computed.  net9.0-browser was computed.  net9.0-ios was computed.  net9.0-maccatalyst was computed.  net9.0-macos was computed.  net9.0-tvos was computed.  net9.0-windows was computed.  net10.0 is compatible.  net10.0-android was computed.  net10.0-browser was computed.  net10.0-ios was computed.  net10.0-maccatalyst was computed.  net10.0-macos was computed.  net10.0-tvos was computed.  net10.0-windows was computed. 
Compatible target framework(s)
Included target framework(s) (in package)
Learn more about Target Frameworks and .NET Standard.

  • net10.0

    • No dependencies.

  • net8.0

    • No dependencies.

NuGet packages

This package is not used by any NuGet packages.

GitHub repositories

This package is not used by any popular GitHub repositories.

Version Downloads Last Updated
1.1.0 96 5/20/2026
1.0.0 114 1/27/2026