Client Hints

Client Hints

Modern Chromium-based browsers increasingly freeze/reduce the information exposed in the User-Agent string and instead expose structured data through User-Agent Client Hints (Sec-CH-UA-* headers). DeviceDetector.NET can combine both sources to improve accuracy.

Client Hints are optional — everything works with just a User-Agent string, but passing Client Hints when available lets the parser prefer more precise brand/version/platform data.

Requesting Client Hints from the browser

Your server must opt in by sending an Accept-CH response header listing the hints it wants:

Accept-CH: Sec-CH-UA-Full-Version-List, Sec-CH-UA-Model, Sec-CH-UA-Platform, Sec-CH-UA-Platform-Version, Sec-CH-UA-Arch, Sec-CH-UA-Bitness, Sec-CH-UA-Mobile, Sec-CH-UA-Form-Factors

On subsequent requests the browser will include the requested hints as headers.

Building a ClientHints instance

ClientHints.Factory builds an instance from any Dictionary<string, string> of headers — it recognizes both the raw HTTP header names and normalized variants (http-sec-ch-ua-model, sec-ch-ua-model, model, ...):

using DeviceDetectorNET;

var headers = Request.Headers.ToDictionary(a => a.Key, a => a.Value.ToArray().FirstOrDefault());
var clientHints = ClientHints.Factory(headers);

var dd = new DeviceDetector(userAgent, clientHints);
dd.Parse();

Headers recognized

Client Hint header	ClientHints property	Meaning
Sec-CH-UA-Arch	Architecture	Underlying CPU architecture
Sec-CH-UA-Bitness	Bitness	Underlying CPU architecture bitness
Sec-CH-UA-Mobile	Mobile	Whether the UA wants a "mobile" UX
Sec-CH-UA-Model	Model	Device model
Sec-CH-UA-Platform	Platform	OS/platform brand
Sec-CH-UA-Platform-Version	PlatformVersion	OS/platform version
Sec-CH-UA-Full-Version	UaFullVersion	Full browser version
Sec-CH-UA-Full-Version-List / Sec-CH-UA	FullVersionList	Brand → version pairs
Sec-CH-UA-Form-Factors	FormFactors	Device form factor names
X-Requested-With	App	Android app package id (when not XMLHttpRequest)

Reading values back

clientHints.IsMobile();
clientHints.GetArchitecture();
clientHints.GetBitness();
clientHints.GetModel();
clientHints.GetOperatingSystem();
clientHints.GetOperatingSystemVersion();
clientHints.GetBrandList();     // IReadOnlyDictionary<string, string>
clientHints.GetBrandVersion();
clientHints.GetApp();
clientHints.GetFormFactors();   // List<string>

Notes

• ClientHints is a straightforward C# port of the PHP DeviceDetector\ClientHints class — behavior (including which header wins when several convey the same information) matches upstream.
• If no relevant headers are present, ClientHints.Factory still returns a valid (empty) instance — pass it in unconditionally, there's no need to branch on whether the client sent hints.