Explain the difference between in-process and out-of-process hosting.

Question

ICSM Computer · Answer

In ASP.NET Core, in-process and out-of-process refer to how your application is hosted and run with respect to the web server (like IIS or Kestrel). Here's a clear breakdown:
In-Process Hosting
The ASP.NET Core app runs inside the IIS worker process (w3wp.exe).No separate process for the Kestrel server is created.Better performance due to avoiding reverse proxy overhead.
Configuration:
In your .csproj file:
andlt;AspNetCoreHostingModelandgt;InProcessandlt;/AspNetCoreHostingModelandgt;
Request Flow:
Browser → IIS (w3wp.exe) → ASP.NET Core Middleware
Pros:
Faster because there is no inter-process communication.Simpler setup – everything runs in a single process.
Cons:
Runs only on Windows with IIS.Limited to IIS features and constraints.
Out-of-Process Hosting
ASP.NET Core app runs in its own process (like dotnet.exe).IIS (or Nginx/Apache) acts as a reverse proxy forwarding requests to the app.
Configuration:
In your .csproj file:
andlt;AspNetCoreHostingModelandgt;OutOfProcessandlt;/AspNetCoreHostingModelandgt;
Request Flow:
Browser → IIS (w3wp.exe) → Kestrel (dotnet.exe) → ASP.NET Core Middleware
Pros:
Cross-platform (Linux, macOS, Windows).Full control over Kestrel and app lifetime.
Cons:
Slight performance penalty due to the proxy hop.More configuration complexity (especially on Linux).
Comparison Table
Feature
In-Process
Out-of-Process
Process
w3wp.exe (IIS worker)
Separate dotnet.exe
Performance
Faster
Slightly slower
OS Support
Windows only
Cross-platform
Reverse Proxy Needed
No
Yes (IIS, Nginx, Apache)
Hosting Model Tag
InProcess
OutOfProcess
When to Use Which?
Use In-Process for Windows + IIS deployments where performance matters.Use Out-of-Process if you:
Need cross-platform supportWant more control over the app processAre using Kestrel behind a reverse proxy

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Explain the difference between in-process and out-of-process hosting.

ICSM Computer

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1 Answers

In-Process Hosting

Configuration:

Request Flow:

Pros:

Cons:

Out-of-Process Hosting

Configuration:

Request Flow:

Pros:

Cons:

Comparison Table

When to Use Which?

Liked By

Feature	In-Process	Out-of-Process
Process	`w3wp.exe` (IIS worker)	Separate `dotnet.exe`
Performance	Faster	Slightly slower
OS Support	Windows only	Cross-platform
Reverse Proxy Needed	No	Yes (IIS, Nginx, Apache)
Hosting Model Tag	`InProcess`	`OutOfProcess`