Kestrel Server

✅ **Kestrel Server in ASP.NET Core

📌 What is Kestrel?

• Kestrel is the default, cross-platform web server included with ASP.NET Core.

• It is:

  • Lightweight

  • High-performance

  • Runs on Windows, Linux, and macOS

✅ Think of Kestrel as the core engine that handles HTTP requests for your ASP.NET Core app.

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🏎️ Why Use Kestrel?

• Faster than traditional web servers like IIS or Apache.

• Ideal for microservices, APIs, and containerized apps.

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🧱 What Kestrel Doesn’t Do (Limitations)

Kestrel does not support some advanced features natively:

• URL Rewriting

• Security configurations

• Request Filtering

• Compression

• Rate Limiting, Load Balancing, etc.

👉 That’s why it’s recommended to use Kestrel behind a reverse proxy like:

• IIS (on Windows)

• Nginx or Apache (on Linux)

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🌐 Protocols Supported by Kestrel

• HTTP/1.1

• HTTP/2

• HTTP/3 (enabled by default in ASP.NET Core 8)

• HTTPS (TLS)

• WebSockets

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🛠️ Built-in Features

• Logging and Diagnostics

• Metrics collection (for observability)

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💡 Fun Fact

The name “Kestrel” comes from a small falcon (bird of prey) known for hovering mid-air while hunting. It symbolizes speed and agility — just like the server.

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📚 Example: Kestrel Usage in Program.cs

var builder = WebApplication.CreateBuilder(args);
 
// Configure Kestrel options (optional)
builder.WebHost.ConfigureKestrel(options =>
{
    options.ListenAnyIP(5000); // HTTP
    options.ListenAnyIP(5001, listenOptions =>
    {
        listenOptions.UseHttps(); // HTTPS
    });
});
 
var app = builder.Build();
 
app.MapGet("/", () => "Hello from Kestrel!");
 
app.Run();

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🛡️ When to Use Reverse Proxy

Use IIS or Nginx in front of Kestrel when you need:

• Advanced security

• Caching

• Load balancing

• Request filtering

• Static file handling

• Enterprise-grade logging and monitoring

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🔚 In Summary

Feature	Kestrel
Cross-platform	✅
High Performance	✅
Production-ready alone	🚫 (better behind reverse proxy)
Supports HTTP/1, 2, 3, HTTPS, WebSockets	✅
Advanced server features	❌ (needs reverse proxy)