Introduction

Every time you start a new ASP.NET project, you face the same question: should I use Minimal APIs or Controllers?

Microsoft introduced Minimal APIs in .NET 6 and has been pushing them hard ever since. The official docs now say "we recommend Minimal APIs" for new projects. But Controllers have been around forever, they work great, and your team already knows them.

So which one should you actually use? Let me cut through the noise and give you a practical answer based on real projects, not marketing material.

What Are Minimal APIs Anyway?

Minimal APIs let you create HTTP endpoints without controllers, routing attributes, or much ceremony at all. Here's a complete API in about 10 lines:

csharp

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapGet("/products", () => 
{
    return new[] 
    { 
        new Product(1, "Laptop"), 
        new Product(2, "Mouse") 
    };
});

app.Run();

record Product(int Id, string Name);

That's it. No controller class. No routing attributes. Just map your endpoints and go.

What About Controllers?

Controllers are the traditional approach. You create classes, add attributes, and structure your code using object-oriented patterns:

csharp

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    [HttpGet]
    public ActionResult<Product[]> GetProducts()
    {
        return new[] 
        { 
            new Product(1, "Laptop"), 
            new Product(2, "Mouse") 
        };
    }
}

record Product(int Id, string Name);

More code, more structure, more familiar to most developers.

The Performance Story

Let's talk about performance first because Microsoft keeps mentioning it.

In .NET 9, Minimal APIs got a huge boost. They can handle 15% more requests per second than .NET 8 and use 93% less memory. That sounds incredible, right?

But here's the context: Minimal APIs are faster than Controllers, but the difference is small. We're talking microseconds per request. In a real benchmark comparing both approaches in .NET 9:

• Minimal API: 61 microseconds per request, 7KB allocated

• Controller: 67 microseconds per request, 12KB allocated

That's about 10% faster and 40% less memory. Good, but not game-changing unless you're running at massive scale.

The bottom line: For 99% of applications, this performance difference won't matter. Your database queries, business logic, and external API calls will dwarf any framework overhead.

When to Use Minimal APIs

Here are the scenarios where Minimal APIs actually shine:

1. Simple Microservices

If you're building small, focused services with a handful of endpoints, Minimal APIs are perfect:

csharp

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddSingleton<IEmailService, EmailService>();

var app = builder.Build();

app.MapPost("/send-email", async (EmailRequest request, IEmailService emailService) =>
{
    await emailService.SendAsync(request.To, request.Subject, request.Body);
    return Results.Ok();
});

app.Run();

Clean, simple, easy to understand. The entire service fits in one file.

2. Quick Prototypes and Demos

When you need to spin up an API quickly for testing or demonstration:

csharp

var app = WebApplication.Create();

app.MapGet("/health", () => "OK");
app.MapGet("/version", () => new { version = "1.0.0" });

app.Run();

No project setup. No folder structure. Just endpoints.

3. Serverless Functions

Minimal APIs work great in Azure Functions or AWS Lambda where cold start time matters. Less code means faster startup.

4. Learning .NET

If you're teaching someone ASP.NET, Minimal APIs remove a lot of ceremony. You can focus on concepts without explaining controllers, attributes, and inheritance.

When to Use Controllers

Controllers are still the better choice for many scenarios:

1. Large Applications with Many Endpoints

Once you have more than 10-15 endpoints, Controllers help you organize your code:

csharp

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    private readonly IProductService _productService;

    public ProductsController(IProductService productService)
    {
        _productService = productService;
    }

    [HttpGet]
    public async Task<ActionResult<IEnumerable<Product>>> GetAll()
    {
        var products = await _productService.GetAllAsync();
        return Ok(products);
    }

    [HttpGet("{id}")]
    public async Task<ActionResult<Product>> GetById(int id)
    {
        var product = await _productService.GetByIdAsync(id);
        if (product == null) return NotFound();
        return Ok(product);
    }

    [HttpPost]
    public async Task<ActionResult<Product>> Create(CreateProductDto dto)
    {
        var product = await _productService.CreateAsync(dto);
        return CreatedAtAction(nameof(GetById), new { id = product.Id }, product);
    }

    [HttpPut("{id}")]
    public async Task<ActionResult> Update(int id, UpdateProductDto dto)
    {
        await _productService.UpdateAsync(id, dto);
        return NoContent();
    }

    [HttpDelete("{id}")]
    public async Task<ActionResult> Delete(int id)
    {
        await _productService.DeleteAsync(id);
        return NoContent();
    }
}

All your product operations live in one class. Easy to find. Easy to test. Easy to maintain.

Try doing this with Minimal APIs and your Program.cs file becomes a nightmare.

2. Teams with Existing Controller Knowledge

If your team has been writing ASP.NET APIs for years, they know Controllers. The patterns are familiar. The testing approaches are established. Don't force a change unless there's a real benefit.

3. Complex Validation and Business Logic

Controllers integrate better with things like action filters, model validation, and custom attributes:

csharp

[ApiController]
[Route("api/[controller]")]
public class OrdersController : ControllerBase
{
    [HttpPost]
    [Authorize]
    [ValidateModel]
    [RateLimit(10, 60)]
    public async Task<ActionResult<Order>> CreateOrder(CreateOrderDto dto)
    {
        // Your validation attributes run automatically
        // Custom logic here
    }
}

With Minimal APIs, you'd need to implement this validation manually or create custom middleware.

4. Swagger/OpenAPI Documentation

While both approaches support OpenAPI, Controllers have better tooling support. Attributes like [ProducesResponseType] work seamlessly:

csharp

[HttpGet("{id}")]
[ProducesResponseType(typeof(Product), 200)]
[ProducesResponseType(404)]
public async Task<ActionResult<Product>> GetById(int id)
{
    // Swagger knows exactly what this returns
}

Minimal APIs can do this too, but it's more verbose.

5. Testing

Controllers are easier to unit test because they're just classes:

csharp

[Fact]
public async Task GetById_ReturnsProduct_WhenProductExists()
{
    // Arrange
    var mockService = new Mock<IProductService>();
    mockService.Setup(s => s.GetByIdAsync(1))
        .ReturnsAsync(new Product(1, "Test"));

    var controller = new ProductsController(mockService.Object);

    // Act
    var result = await controller.GetById(1);

    // Assert
    var okResult = Assert.IsType<OkObjectResult>(result.Result);
    var product = Assert.IsType<Product>(okResult.Value);
    Assert.Equal("Test", product.Name);
}

Testing Minimal APIs requires more setup and often involves integration tests rather than unit tests.

The Real-World Decision

Here's how I actually make this decision on real projects:

Choose Minimal APIs if:

• You have less than 10 endpoints

• It's a microservice doing one specific thing

• Speed of development matters more than structure

• You're prototyping or building a POC

Choose Controllers if:

• You have more than 10 endpoints

• Multiple developers will work on the codebase

• You need complex authorization or validation

• Your team already knows Controllers well

• It's a long-term enterprise application

Can You Mix Both?

Yes! Nothing stops you from using both in the same project:

csharp

var builder = WebApplication.CreateBuilder(args);

// Add controllers
builder.Services.AddControllers();

var app = builder.Build();

// Add a minimal API endpoint
app.MapGet("/health", () => "OK");

// Map controllers
app.MapControllers();

app.Run();

Use Controllers for your main API and Minimal APIs for simple utility endpoints like health checks or webhooks.

The Migration Question

If you have an existing Controller-based API, should you migrate to Minimal APIs?

My answer: No. Unless you have a specific reason (like reducing cold start times for serverless), migration is just busywork. Your existing API works fine. Spend your time on features instead.

Microsoft isn't deprecating Controllers. They're not going away. The docs say Minimal APIs are "recommended," not "required."

My Recommendation

For new projects in 2025, I'd start with Controllers by default. They give you better structure and organization as your API grows. The performance difference doesn't matter for most apps, and the development experience is more productive once you get past the initial setup.

Use Minimal APIs when you have a specific reason: it's genuinely small and simple, you need maximum performance, or you're building something quick and disposable.

Don't let the marketing push you into Minimal APIs just because they're newer. Use the right tool for your specific situation.

Quick Reference

Here's a side-by-side comparison:

Wrapping Up

The Minimal APIs vs Controllers debate isn't about which is better in absolute terms. It's about which is better for your specific project, team, and requirements.

Minimal APIs are great for small, simple services. Controllers are great for everything else. Both are fully supported, both work well, and both will be around for years.

Pick the one that makes sense for your situation and move on to building actual features. That's what matters.