Serilog.Enrichers.AspNetCore.DeviceDetector

Serilog.Enrichers.AspNetCore.DeviceDetector

A Serilog enricher that attaches device, client, operating system, brand and model information — parsed from the current ASP.NET Core request's User-Agent header via DeviceDetector.NET — to every log event written while handling that request.

Install

dotnet add package Serilog.Enrichers.AspNetCore.DeviceDetector

Targets net8.0, net9.0 and net10.0. Depends on Serilog, Serilog.AspNetCore, and (via project reference) DeviceDetector.NET itself.

Setup

Register IHttpContextAccessor, then wire the enricher into Serilog through UseSerilog, passing the app's IServiceProvider so it can resolve the accessor:

using Serilog;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddHttpContextAccessor();

builder.Host.UseSerilog((context, services, configuration) => configuration
    .ReadFrom.Configuration(context.Configuration)
    .Enrich.WithDeviceDetector(services)
    .WriteTo.Console());

var app = builder.Build();

AddHttpContextAccessor() is required. WithDeviceDetector(IServiceProvider) calls serviceProvider.GetRequiredService<IHttpContextAccessor>() internally — if you forget to register it, you'll get a clear DI resolution exception at startup rather than a silent no-op.

What you get

Every log event emitted while an HttpContext is active gets a structured DeviceDetector property containing the parsed device/client/OS/brand/model result (the same shape as DeviceDetector.GetInfoFromUserAgent — see Getting Started). Because the property is destructured, structured sinks (Seq, Elasticsearch, JSON file sinks, etc.) expose it as queryable sub-fields rather than one opaque string.

{
  "DeviceDetector": {
    "UserAgent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) ...",
    "DeviceType": "desktop",
    "OsFamily": "Windows",
    "BrowserFamily": "Chrome",
    "Client": { "Name": "Chrome", "Version": "128.0.0.0", "...": "..." },
    "Os": { "Name": "Windows", "Version": "10", "...": "..." }
  }
}

Per-request caching

The User-Agent is parsed at most once per request, not once per log call: the first Enrich call for a request runs DeviceDetector.GetInfoFromUserAgent and stores the resulting Serilog property on HttpContext.Items; every subsequent log event in the same request reuses that stored property instead of re-parsing. This is covered by a dedicated test (Enrich_ReusesCachedProperty_ForSubsequentEventsInSameRequest) in Serilog.Enrichers.AspNetCore.DeviceDetector.Tests.

This cache is scoped to HttpContext.Items, so it's automatically request-scoped and requires no manual setup or cleanup — unlike the general-purpose caching layers DeviceDetector.NET otherwise offers, you don't need to configure anything here to avoid redundant parsing within a request.

VersionTruncation.VERSION_TRUNCATION_NONE is forced for this parse, regardless of what DeviceDetector.SetVersionTruncation is set to elsewhere in your app — logs always get full version numbers.

No-op cases

The enricher silently does nothing (adds no property) when:

• There is no active HttpContext — e.g. during startup, in a hosted/background service, or in code running outside a request.
• The request has no User-Agent header.

This makes it safe to leave configured globally; it only ever adds information, never throws for missing context.

Relationship to the demo API and DI wrapper

This enricher solves logging, specifically. If you need parsed device info in application logic (not just attached to logs), see ASP.NET Core Integration for the demo HomeController pattern and the dependency-injection wrapper written in response to issue #83 — the two are independent and commonly used together (one enriches logs, the other drives behavior).