RobotsTxtCore 2.1.1

.NET 5.0 .NET Core 3.1
dotnet add package RobotsTxtCore --version 2.1.1
NuGet\Install-Package RobotsTxtCore -Version 2.1.1
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="RobotsTxtCore" Version="2.1.1" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add RobotsTxtCore --version 2.1.1
#r "nuget: RobotsTxtCore, 2.1.1"
#r directive can be used in F# Interactive, C# scripting and .NET Interactive. Copy this into the interactive tool or source code of the script to reference the package.
// Install RobotsTxtCore as a Cake Addin
#addin nuget:?package=RobotsTxtCore&version=2.1.1

// Install RobotsTxtCore as a Cake Tool
#tool nuget:?package=RobotsTxtCore&version=2.1.1

RobotsTxtCore NuGet Badge

A Robots.txt middleware for ASP.NET Core. Why is this needed you ask? Because if you need to add dynamic values (such as a configured url from your CMS) you'll need some sort of code to handle that, and this makes it easy.


.Net CLI

> dotnet add package RobotsTxtCore


PM> Install-Package RobotsTxtCore

Changes from 1.0 to 2.0

The first version of this package was only a middleware and had to be configured in the Configure method in the Startup class. This felt fine at the time but as more and more things moved to having configuration as a service and then letting the middleware consume the service I felt like this package got outdated.

So I've made a breaking change and made the middleware consume a IRobotsTxtProvider which in turn takes care of configuration. There is a default provider for static uses (i.e. exactly what the old one did) but doing it this way also let me optimize it quite a lot. A quick benchmark shows that running a thousand requests against /robots.txt is now done in 25% of the time while also lowering allocations about the same.

NuGetReferences Mean Error StdDev Gen 0 Gen 1 Allocated
RobotsTxtCore 1.1.0 1,169.2 μs 22.62 μs 27.77 μs 691.4063 1.9531 4,242 KB
RobotsTxtCore 2.0.0-preview1 419.8 μs 3.88 μs 3.24 μs 167.9688 - 1,031 KB
RobotsTxtCore 2.0.0-preview2 431.5 μs 2.90 μs 2.57 μs 150.3906 - 922 KB
RobotsTxtCore 2.0.0-preview3 307.4 μs 2.00 μs 1.87 μs 155.2734 - 953 KB

Sure, it was really fast to start with and there are very few sites where /robots.txt gets a ton of traffic but that doesn't mean it's not worth it 😉.

Introducing the IRobotsTxtProvider also allows for easier dynamic usage, like reading settings from a database or switching depending on which environment the code is executing in.


To specify multiple rules with the fluent interface makes it really easy.

public void ConfigureServices(IServiceCollection services) {
    services.AddStaticRobotsTxt(builder =>
            .AddSection(section =>
                    .AddComment("Allow Googlebot")
            .AddSection(section =>
                    .AddComment("Disallow the rest")

public void Configure(IApplicationBuilder app) {


# Allow Googlebot
User-agent: Googlebot
Allow: /

# Disallow the rest
User-agent: *
Disallow: /
Crawl-delay: 10


Or if you just want to deny everyone.

public void ConfigureServices(IServiceCollection services) {
    services.AddStaticRobotsTxt(builder =>

public void Configure(IApplicationBuilder app) {


User-agent: *
Disallow: /


IRobotsTxtProvider allows for dynamicly configuring the Robots.txt output depending on your case. It could be used to read from config, to check a database setting or perhaps which environment your application is currently running in.

public class CoolRobotsTxtProvider : IRobotsTxtProvider {
    private readonly CoolContext _context;

    public CoolRobotsTxtProvider(CoolContext context) {
        _context = context;

    public async Task<RobotsTxtResult> GetResultAsync(CancellationToken cancellationToken) {
        var settings = await _context.Settings.FirstAsync();

        var builder = new RobotsTxtOptionsBuilder();

        RobotsTxtOptions options;
            options = builder.AllowAll().Build();
            options = builder.DenyAll().Build();

        var content = options.ToString();
        var buffer = Encoding.UTF8.GetBytes(content).AsMemory();
        return new RobotsTxtResult(buffer, settings.RobotsTxtMaxAge);
Product Versions
.NET net5.0 net5.0-windows net6.0 net6.0-android net6.0-ios net6.0-maccatalyst net6.0-macos net6.0-tvos net6.0-windows net7.0 net7.0-android net7.0-ios net7.0-maccatalyst net7.0-macos net7.0-tvos net7.0-windows
.NET Core netcoreapp3.1
Compatible target framework(s)
Additional computed target framework(s)
Learn more about Target Frameworks and .NET Standard.
  • .NETCoreApp 3.1

    • No dependencies.
  • net5.0

    • No dependencies.
  • net6.0

    • No dependencies.

NuGet packages (2)

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Version Downloads Last updated
2.1.1 14,792 6/24/2022
2.0.0 34,872 11/18/2021
2.0.0-preview3 302 9/11/2021
2.0.0-preview2 225 9/9/2021
2.0.0-preview1 206 9/9/2021
1.1.0 193,189 8/11/2019
1.0.1 5,929 2/27/2018
1.0.0 767 2/24/2018
1.0.0-beta-2 831 1/2/2018
1.0.0-beta-1 790 12/29/2017