MyCSharp.HttpClientHints

Reading HTTP Client Hints with .NET

NuGet

NuGet

Client Hints

HTTP client hints are intended to completely replace the user agents (see mycsharp/HttpUserAgentParser) of the browser in the long term and pay more attention to data protection. We are currently in a phase in which client hints are generally regarded as expiremental and therefore do not represent a complete alternative.

Furthermore, in contrast to the User-Agent header, not all client hints are provided automatically, but only on request after the first response from the client.

Usage

The basic idea behind the implementation of MyCSharp.HttpClientHints is to have as little impact as possible on performance and middleware. The options are therefore registered solely via a simple configuration

// Add Http Client Hint Options
builder.Services.AddHttpClientHints(options =>
  {
      options.UserAgent = true;
      options.Platform = true;
      options.Architecture = true;
      options.Device = true;
      options.Mobile = true;
      options.Lifetime = TimeSpan.FromDays(31);
  });

The corresponding headers are set by middleware, which must also be registered.

...
app.UseHttpsRedirection();

// Register Http Client Hints Middleware
app.UseHttpClientHints();

app.UseRouting();
...

The client hints are not read by a separate dependency injection registration, but as an extension method to the header collection or to the HttpContext object.

using MyCSharp.HttpClientHints.AspNetCore;

HttpClientHints clientHints = HttpClientHintsHttpContextExtensions.GetClientHints(httpContext);

Since potentially all client hints are optional, all properties are potentially nullable, which means that the client has not provided this data.

Customization

The Additional property can be used to define your own headers that are to be requested.

// Add Http Client Hint Options
builder.Services.AddHttpClientHints(options =>
  {
      options.UserAgent = true;
      options.Platform = true;
      options.Architecture = true;
      options.Device = true;
      options.Mobile = true;
      options.Additional = ["Sec-CH-UA-Bitness"];
      options.Lifetime = TimeSpan.FromDays(31);
  });

The HttpClientHints object has a reference to all headers received, making it very easy to read them out. Optionally, you can also inherit from the HttpClientHints class itself to simplify access.

HttpClientHints clientHints = HttpClientHintsHttpContextExtensions.GetClientHints(httpContext);
clientHints.Headers.TryGetValue("Sec-CH-UA-Bitness", out StringValues bitness);

Benchmark

BenchmarkDotNet v0.15.2, Windows 10 (10.0.19045.6216/22H2/2022Update)
AMD Ryzen 9 9950X 4.30GHz, 1 CPU, 32 logical and 16 physical cores
.NET SDK 10.0.100-preview.7.25380.108
  [Host]    : .NET 10.0.0 (10.0.25.38108), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
  .NET 10.0 : .NET 10.0.0 (10.0.25.38108), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
  .NET 8.0  : .NET 8.0.19 (8.0.1925.36514), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
  .NET 9.0  : .NET 9.0.8 (9.0.825.36511), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI


| Method                                                 | Job       | Runtime   | Mean      | Error    | StdDev   | Gen0   | Allocated |
|------------------------------------------------------- |---------- |---------- |----------:|---------:|---------:|-------:|----------:|
| 'View: read few properties (no alloc)'                 | .NET 8.0  | .NET 8.0  |  31.26 ns | 0.403 ns | 0.377 ns |      - |         - |
| 'View: read few properties (no alloc)'                 | .NET 9.0  | .NET 9.0  |  34.50 ns | 0.328 ns | 0.307 ns |      - |         - |
| 'View: read few properties (no alloc)'                 | .NET 10.0 | .NET 10.0 |  21.71 ns | 0.397 ns | 0.371 ns |      - |         - |
|                                                        |           |           |           |          |          |        |           |
| 'View: BuildSnapshot (alloc 1)'                        | .NET 8.0  | .NET 8.0  |  70.83 ns | 1.058 ns | 0.884 ns | 0.0052 |      88 B |
| 'View: BuildSnapshot (alloc 1)'                        | .NET 9.0  | .NET 9.0  |  67.35 ns | 0.462 ns | 0.409 ns |      - |         - |
| 'View: BuildSnapshot (alloc 1)'                        | .NET 10.0 | .NET 10.0 |  44.59 ns | 0.599 ns | 0.561 ns |      - |         - |
|                                                        |           |           |           |          |          |        |           |
| 'Extension: GetClientHints(headers) (alloc 1)'         | .NET 8.0  | .NET 8.0  |  70.32 ns | 0.872 ns | 0.816 ns | 0.0052 |      88 B |
| 'Extension: GetClientHints(headers) (alloc 1)'         | .NET 9.0  | .NET 9.0  |  67.24 ns | 0.506 ns | 0.473 ns |      - |         - |
| 'Extension: GetClientHints(headers) (alloc 1)'         | .NET 10.0 | .NET 10.0 |  46.50 ns | 0.254 ns | 0.212 ns |      - |         - |
|                                                        |           |           |           |          |          |        |           |
| 'Extension: GetClientHints(context) (alloc 1, cached)' | .NET 8.0  | .NET 8.0  | 111.04 ns | 0.767 ns | 0.718 ns | 0.0052 |      88 B |
| 'Extension: GetClientHints(context) (alloc 1, cached)' | .NET 9.0  | .NET 9.0  | 114.79 ns | 2.304 ns | 2.155 ns | 0.0052 |      88 B |
| 'Extension: GetClientHints(context) (alloc 1, cached)' | .NET 10.0 | .NET 10.0 |  98.26 ns | 1.429 ns | 1.267 ns | 0.0052 |      88 B |

Samples

ASP.NET Core MVC Sample

Maintained

by @BenjaminAbt and @gfoidl

License

MIT License

Copyright (c) 2024-2025 MyCSharp

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

License

mycsharp/HttpClientHints

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