Tutorials ASP.NET Core Web API Tutorial
ASP.NET Core Kestrel Web Server — Complete Guide
ASP.NET Core Kestrel Web Server — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of ASP.NET Core Web API Tutorial on Toolliyo Academy.
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ASP.NET Core Web API Tutorial · Lesson 23 of 175
ASP.NET Core Kestrel Web Server
Beginner → Intermediate → Advanced → Professional
Beginner · 1 — Setup & foundations · ~6 min · Module 2: Web API Basics
What is this?
Kestrel is the built-in cross-platform web server in ASP.NET Core. It listens on ports (e.g. 5001 HTTPS) and forwards requests into middleware and controllers.
Why should you care?
Interviewers ask Kestrel vs IIS. Answer: Kestrel handles HTTP; IIS or Nginx can reverse-proxy in production.
See it live — copy this example
Create a Web API (dotnet new webapi), paste the example, run dotnet run, test in Swagger.
// launchSettings.json — applicationUrl
"https://localhost:7001;http://localhost:5001"
// Program.cs
app.Run(); // Kestrel starts listeningRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- In development Kestrel alone is enough.
- In production, IIS or Nginx terminates TLS and proxies to Kestrel (out-of-process) or hosts in-process.
Try it yourself
- Run dotnet run and note URLs in console.
- Change applicationUrl in launchSettings.json.
- Hit /swagger and confirm Kestrel responds.
- Change a route URL or DTO property and save — test again in Swagger or curl.
- Return the wrong status code on purpose (404 instead of 200) and see what the client shows.
Remember
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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