Minimal APIs in .NET 8

8/16/2025

Everything You Need to Know About Minimal APIs in .NET

Minimal APIs are a lightweight approach to building web APIs in the .NET ecosystem with minimal boilerplate. First introduced in ASP.NET Core 6, they have evolved through .NET 7 and .NET 8 to become a mainstream way of creating HTTP services. This article provides a technical deep dive into Minimal APIs, comparing them with traditional MVC controllers, exploring performance benefits, and highlighting modern .NET best practices for using them. By the end, architects and developers will understand why Minimal APIs are gaining popularity and how to leverage them for high-performance, scalable solutions.

What Are Minimal APIs in .NET?

Minimal APIs are a simplified programming model for building RESTful APIs in ASP.NET Core with far less ceremony than the traditional controller-based approach. In essence, a Minimal API application can be boiled down to just a few lines of code: configuring a web application and mapping HTTP endpoints directly to inline handlers or small functions. For example, a “Hello World” Minimal API in .NET looks like this:

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

app.MapGet("/", () => "Hello, World!");

app.Run();

In this model, you don’t need to define controller classes or use extensive attributes for routing. Instead, routes are defined explicitly via methods like MapGet, MapPost, etc., on the WebApplication object. This approach strips away much of the boilerplate and configuration that ASP.NET developers might be used to, focusing on brevity and clarity. Minimal APIs were designed to make building microservices and small web APIs easier, but they are capable of powering larger applications as well, as we’ll discuss.

Why Choose Minimal APIs? (Benefits and Use Cases)

Minimal APIs come with several benefits that make them attractive for modern application development:

Simplicity & Productivity: Minimal APIs prioritize clear and concise code. With far less setup and ceremony, developers can achieve more with less code. This simplicity accelerates development and lowers the barrier to entry for building APIs. The lightweight syntax (as shown in the example above) makes it beginner-friendly, yet it's also appreciated by experienced developers for quickly stubbing out services.
Reduced Boilerplate & Configuration: There’s no need for writing controller classes, defining routes via attributes, or adding extra files for simple endpoints. This streamlined development means you can focus on core business logic rather than framework code. By minimizing abstractions and default middleware, Minimal APIs reduce overhead and let you avoid unnecessary components.
High Performance: Performance has been a central focus of the .NET team, and Minimal APIs reflect that emphasis. By cutting out the conventional MVC pipeline (which involves many steps for processing a request, including routing, model binding, filters, etc.), Minimal APIs handle requests with less overhead. In practice, this can translate to faster execution and lower latency for HTTP calls. Benchmarks commonly show that Minimal APIs tend to be slightly faster and use less memory than equivalent controller endpoints due to the leaner request processing pipeline. This performance gap isn’t huge for simple scenarios, but it is measurable – Minimal APIs generally outperform controllers in lightweight operations, which makes them ideal for microservices, IoT backends, and other high-throughput scenarios.
Explicitness & Maintainability: Minimal APIs favor an explicit programming style over the “magic” of conventions. Routes are defined in code explicitly, which makes it clear what endpoints exist and how they behave. This can improve maintainability for teams: new developers can open the Program.cs (or whatever file sets up the endpoints) and see all route definitions in one place. This explicit approach reduces the chance of subtle bugs that sometimes occur with attribute routing and hidden conventions. It also tends to make debugging easier, since there's no framework automagic determining which method gets called – you’ve defined it all directly.
Flexibility & Modern Features: With Minimal APIs, you opt-in to the features you need. Unlike MVC, which is “opt-out” (always running a full filter and model-binding pipeline for each request even if you don’t need it), Minimal APIs let you start simple and add functionality as required. You can integrate middleware, model binding, validation, authentication, etc., but you bring in only what the API needs – a “pay for play” model. This makes them very flexible and allows tailoring the API for specific requirements. Modern ASP.NET Core improvements are fully available: for example, .NET 7 introduced features like endpoint filters (a lightweight alternative to action filters) to Minimal APIs, and .NET 8 added support for form-data binding and antiforgery tokens in Minimal APIs. Additionally, Minimal APIs benefit from improved async/await handling, route groups, and other enhancements in the latest .NET versions.
Scalability & Suitability for Microservices: Don’t be misled by the name – Minimal APIs can scale to large applications. They are particularly well-suited for microservice architectures, where each service is small and focused. In fact, the minimal overhead and quick startup of these APIs make them a great fit for containerized microservices or serverless functions, where cold-start time and resource utilization need to be minimal. Minimal APIs have been used to build everything from simple CRUD services to enterprise-grade systems. They also shine in scenarios like IoT, mobile backends, or real-time services that require fast, lightweight endpoints.
Alignment with Modern .NET and Future Trends: The design of Minimal APIs aligns with modern .NET trends such as vertical slice architecture (organizing code by feature) and even native AOT (ahead-of-time compilation). ASP.NET Core is moving towards better Native AOT support, and the traditional MVC controllers (which rely on runtime discovery and reflection) are not fully compatible with AOT optimizations. Minimal APIs, being more explicit and requiring fewer reflective operations, are more friendly to these AOT scenarios, which can result in much faster startup times and smaller deployment sizes. This makes Minimal APIs a future-proof choice as .NET evolves.

In summary, Minimal APIs are ideal when you want a fast, concise, and easy-to-maintain API. They particularly excel for high-performance microservices or any scenario where you want to eliminate unnecessary overhead. Next, we’ll look at how they compare in detail to the familiar MVC controller approach.

Minimal APIs vs. Traditional Controllers (Modern Approach vs MVC)

One of the key questions teams ask is how Minimal APIs differ from the traditional ASP.NET Core MVC controller pattern. Both approaches can achieve the same end result – building a RESTful API – but there are important differences in style, flexibility, and performance:

Routing and Explicitness: In MVC, routing is often driven by attributes ([HttpGet], [Route], etc.) or by naming conventions (e.g. a controller named ProductsController with an action Get implicitly maps to a GET /products endpoint). This convention-based routing can sometimes be unclear, especially in large projects with many controllers and actions – you might not immediately know what routes are defined without scanning multiple files. In Minimal APIs, routes are defined explicitly in code via MapGet, MapPost, etc., including the full URL pattern (e.g. app.MapGet("/products/{id}", ...)). This means no hidden conventions – it’s very clear which endpoints exist and which HTTP verbs they handle. The explicit mapping can make it easier to understand and debug the API’s behavior. There is less “magic” – what you see is what you get.
Pipeline and Overhead: A traditional ASP.NET Core controller goes through a full middleware and MVC pipeline for each request. This pipeline includes routing, model binding (which tries to bind query params, route params, body, etc. to method parameters or model objects), executing filters (authorization filters, action filters, etc.), then executing the controller action, and possibly result filters. It’s powerful but comes with overhead. Minimal APIs, on the other hand, allow you to skip parts of this pipeline by default, only adding what you explicitly need. For example, if you want model binding, you can simply accept a complex object in your route handler and ASP.NET Core will deserialize the JSON body for you – but it won’t run elaborate model-binding logic unless you opt in. If you need validation or filters, you can add endpoint filters or manually call validation logic. In short, MVC is opt-out, whereas Minimal APIs are opt-in. This opt-in model means a leaner request through the system, which is why Minimal APIs tend to use fewer resources per request.
Dependency Injection Style: Both controllers and Minimal APIs use the same underlying DI (dependency injection) container in ASP.NET Core. In controllers, dependencies are typically taken via constructor injection. In Minimal APIs, since there are no controller classes, you simply declare dependencies as parameters in the handler lambda or method. For example, app.MapGet("/hello", (IGreetingService svc) => svc.GetMessage()); will automatically resolve IGreetingService from DI for each request. This is a very convenient pattern – you get per-request DI without the ceremony of a constructor. It can also make testing easier in some cases, since each endpoint handler is just a function that can be called with mocked dependencies if needed. Controllers can accumulate many dependencies, which can make them harder to unit test in isolation. Minimal API endpoints encourage smaller, focused handlers that take only what they need for that operation, which can improve testability and reduce complexity.
Organization of Code: In the MVC approach, you typically organize code by controllers (and sometimes by areas or feature folders), with each controller holding multiple related endpoints. Minimal APIs initially give the impression that you might end up putting all your endpoints in one file (Program.cs), which would get unwieldy. However, the modern best practice is to organize Minimal API endpoints by feature as well – often using extension methods or separate static classes to group routes. For example, you might have a WeatherForecastEndpoints class with a static Map method to register all routes related to weather forecasting. In .NET 7+, you can also use Route Groups (app.MapGroup("/weather")) to group related endpoints under a common prefix and even attach common middleware or filters to that group. This way, Minimal API projects can be structured in a clean, maintainable way that scales to large applications, similar to how controllers are split across multiple files. The key difference is you have flexibility to organize by feature slices or other architectures (vertical slice, Clean Architecture, etc.) without being constrained to the controller paradigm. Minimal APIs work nicely with domain-driven designs – they don’t force a specific layering, and you can still keep services, repositories, and other layers if desired; only the endpoint definitions are different.
Feature Set and Extensibility: Traditional controllers come with a rich set of features out-of-the-box: built-in model binding for complex types, automatic validation of data annotations, support for return types that automatically produce various HTTP responses, action filters, etc. Minimal APIs started smaller, but have been steadily gaining more features with each .NET release. As of .NET 8, Minimal APIs support binding from route, query, header, body, and form posts; they support validation (via manual calls or using libraries like FluentValidation); and they have constructs like TypedResults (to help return standardized HTTP results) and endpoint filters to mimic the capabilities of action filters. Essentially, anything you can do in a controller can be done in a Minimal API – but it might require a different approach. For example, instead of using [Authorize] attributes on controllers, with Minimal APIs you might use app.UseAuthentication(); app.UseAuthorization(); globally or apply an authorization rule to a specific endpoint or group. The difference is mostly in style, not in capability. Minimal APIs give you “just the pieces you need,” whereas controllers provide a lot of functionality by default. For small to medium APIs, Minimal APIs often hit a sweet spot of having everything needed without the bloat. For very large, complex apps with many cross-cutting concerns, some teams might still prefer the structure of controllers and the myriad of features they bring – but even in those cases, you can mix both approaches in the same project if needed (ASP.NET Core allows mixing controllers and minimal endpoints in one app).

In summary, Minimal APIs vs Controllers comes down to explicit vs conventional, lightweight vs feature-rich. Minimal APIs embrace modern trends of minimalism and explicit mapping, often resulting in simpler and faster endpoints, while controllers carry the legacy of a more expansive framework that may be overkill for certain scenarios. Given the push towards performance and cloud-native microservices in recent years, Minimal APIs offer a timely solution that resonates with those goals.

Building a Minimal API: Getting Started Example

To better illustrate how Minimal APIs work, let’s walk through a quick example of building a simple API with them (using modern .NET syntax and best practices). Suppose we want to create a small API for managing products in a catalog.

First, create a new ASP.NET Core project with Minimal APIs enabled. Using the .NET CLI:

dotnet new web -n ProductApiDemo

If you’re using an IDE template (e.g., Visual Studio), uncheck “Use controllers” so it sets up a minimal API template. In a minimal API project, the main entry point is typically the Program.cs file (with top-level statements). You’ll find no Controllers folder by default.

Let’s set up the basics in Program.cs:

var builder = WebApplication.CreateBuilder(args);

// Add services to the container (e.g., for DI)
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen(); // if you want Swagger/OpenAPI docs

var app = builder.Build();

// Configure middleware (if needed)
app.UseSwagger();
app.UseSwaggerUI();

// Define a simple in-memory data store (demo purposes only)
var products = new List<Product>();
products.Add(new Product { Id = 1, Name = "Widget", Price = 9.99M });

// Map endpoints
app.MapGet("/products", () => Results.Ok(products));

app.MapGet("/products/{id}", (int id) => {
    var product = products.FirstOrDefault(p => p.Id == id);
    return product is not null ? Results.Ok(product) : Results.NotFound();
});

app.MapPost("/products", (Product newProduct) => {
    newProduct.Id = products.Any() ? products.Max(p => p.Id) + 1 : 1;
    products.Add(newProduct);
    return Results.Created($"/products/{newProduct.Id}", newProduct);
});

app.Run();

record Product(int Id, string Name, decimal Price);

In this snippet, we used MapGet and MapPost to define three endpoints: one to get all products, one to get by id, and one to create a product. We directly use minimal API features like Results.Ok(...) and Results.Created(...) to return HTTP responses. Note a few things:

We added EndpointsApiExplorer and SwaggerGen to generate OpenAPI documentation (Swagger). Minimal APIs can be documented just like controllers – if you include these services, they’ll auto-generate docs for your endpoints so you can use Swagger UI to test them.
We didn’t explicitly add any model-binding attributes. In the POST endpoint, we accept a Product newProduct parameter. In Minimal APIs, a complex object like that is automatically bound from the JSON request body by default (as long as the request has the appropriate Content-Type: application/json). Similarly, our GET-by-id endpoint takes an int id parameter, which is automatically bound from the {id} route segment in the URL.
We used helper results like Results.NotFound() and Results.Created() to make intent and status codes explicit. In .NET 7+, there are also TypedResults (e.g., TypedResults.Ok<Product>(product)) that give compile-time types if you prefer that style.

This example is very basic but shows how quick it is to set up a working API. Run it with dotnet run and you’ll have a functioning web API. The code is minimal – no separate files for controllers, no annotations – yet it’s fully functional.

Dependency Injection and Middleware in Minimal APIs

Even though Minimal APIs favor a simple, top-level approach, they still have full access to ASP.NET Core’s powerful features like Dependency Injection (DI) and Middleware. The difference is largely in how you use them:

Dependency Injection: Any services you register with builder.Services can be injected into a Minimal API handler by simply listing them as parameters. For example, if we had an IProductService that our endpoints should use instead of directly manipulating a list, we could register it and then use it in the endpoint:
```
builder.Services.AddSingleton<IProductService, ProductService>();
// ...
app.MapGet("/products/{id}", (int id, IProductService svc) => {
    var product = svc.GetById(id);
    return product is not null ? Results.Ok(product) : Results.NotFound();
});

public interface IProductService
{
    Product? GetById(int id);
}

public sealed class ProductService : IProductService
{
    private readonly List<Product> _data = new()
    {
        new Product(1, "Widget", 9.99m)
    };

    public Product? GetById(int id) => _data.FirstOrDefault(p => p.Id == id);
}
```
Here, IProductService svc is automatically provided by the DI container. This shows how Minimal APIs cleanly integrate with DI. No [FromServices] attributes are needed – the framework can differentiate DI services from route/query parameters by their types and context. ASP.NET Core will try to bind parameters from the route or query first (for simple types like int, string, etc.), and if it sees a parameter that is a complex reference type or an interface/class that is registered in DI, it will inject the service instance. This convention makes Minimal API handler signatures very concise and clear.
Middleware Pipeline: Minimal APIs use the same middleware pipeline configuration as any ASP.NET Core app. You can call app.Use... for any middleware (authentication, logging, CORS, etc.) before mapping endpoints. In a minimal API app, routing is configured implicitly by the minimal host, and app.Run() finalizes endpoint mapping. You still add things like app.UseAuthentication(), app.UseAuthorization(), app.UseCors(), etc., as needed. You can also use custom middleware with app.Use(async (context, next) => { /* ... */ await next(); }); when you need to manipulate the HTTP context directly.
Filters and Validation: In controller-based APIs, you might use filters or action attributes for concerns like validation (e.g., a [ValidateModel] filter) or logging. In Minimal APIs, similar functionality can be achieved either via endpoint filters or by structuring code to handle those concerns. For instance, you can write an endpoint filter that runs before the handler and checks model state or applies an authorization policy. You can also leverage libraries like FluentValidation by manually invoking validators inside handlers or integrating with filters. The key point is that Minimal APIs are not lacking in these capabilities; they simply accomplish them in a more explicit, code-driven way rather than relying on attributes.

In practice, you can build sophisticated pipelines with Minimal APIs. You might have global middleware for error handling or request logging, and use DI for database contexts, logging, etc., just as you would in any ASP.NET Core app. The development experience remains consistent with the rest of the framework.

Performance Highlights of Minimal APIs

One of the primary goals (and biggest selling points) of Minimal APIs is improved performance and reduced overhead. Highlights include:

Lean Request Pipeline: Minimal APIs avoid the full MVC machinery unless you add it back. By default, a minimal endpoint invocation is a fairly direct call through the routing layer to your handler delegate. There’s no controller instantiation, no model binding costs for parameters you didn’t ask for, and fewer allocations overall. This “pay for play” design is intentional – by breaking apart the old MVC monolith, the ASP.NET Core team enabled a scenario where if you just need a simple endpoint, you incur minimal overhead. This is one reason Minimal APIs tend to handle more requests per second compared to controllers in benchmarks.
Benchmark Results: Benchmarks comparing Minimal APIs and controllers commonly show Minimal APIs are a bit faster. For example, simple GET endpoints in Minimal APIs often show a few percent lower latency and fewer allocations than equivalent controller actions. The performance difference tends to narrow as endpoint complexity increases (since business logic dominates), but the baseline overhead savings are real.
Throughput and Scalability: Because of lower per-request overhead, a Minimal API can often achieve slightly better throughput (requests per second) especially on smaller VM instances or containers where memory and CPU are constrained. Fewer allocations mean less GC pressure, and fewer CPU cycles per request mean you can handle more concurrent requests on the same hardware. Minimal APIs also tend to have slightly faster startup times, which can benefit serverless scenarios or frequent scale operations.
Native AOT Compatibility: Minimal APIs are more amenable to Native AOT compilation (as of .NET 7/8). AOT can dramatically improve startup time and reduce memory usage by producing a self-contained native executable. Traditional controller-heavy apps rely more on reflection, making AOT trickier; Minimal APIs are simpler and more explicit, making AOT readiness easier.

In summary, Minimal APIs provide performance benefits primarily by cutting out unneeded overhead. They achieve slightly better raw performance than controllers and use less memory per request, which scales in favor of minimal when you need to handle a large number of simple requests quickly.

Best Practices for Using Minimal APIs (Modern .NET Guidance)

To get the most out of Minimal APIs in a production application, consider the following best practices and tips that align with modern .NET development:

Organize By Feature, Not By Framework: As your Minimal API grows, avoid dumping all routes in a single Program.cs. Instead, structure your project in a feature-centric way. Create separate classes or files for each area of your API (customers, orders, products, etc.), and use extension methods or static classes to add their endpoints. Call something like app.MapCustomerEndpoints() in your Program. .NET 7’s route grouping helps: var customers = app.MapGroup("/customers"); customers.MapGet("{id}", GetCustomer); neatly scopes routes.
Keep Handlers Focused and Use Services: It’s easy with Minimal APIs to accidentally write a lot of logic in the lambda for an endpoint. Resist that urge for anything beyond trivial logic. Treat the minimal endpoint as the orchestrator that calls into your service or domain layer. This separation keeps your code testable and respects single responsibility.
Leverage Typed Results and Status Codes: Use Results.* or TypedResults to make your intent and status codes explicit (Results.NotFound(), Results.Created(), Results.NoContent(), etc.). Returning clear, conventional HTTP responses improves client experience and code readability.
Use Validation and Error Handling: Implement validation for inputs (e.g., FluentValidation) and consistent error handling (e.g., global exception middleware and Results.Problem(...)). Even without controllers, you should return helpful error payloads (such as RFC 7807 ProblemDetails) to clients.
Secure Your Endpoints: Use app.UseAuthentication() and app.UseAuthorization() and apply authorization to individual endpoints or route groups (RequireAuthorization()). Configure CORS when your API is consumed by browsers.
Document Your API: Enable Swagger/OpenAPI with AddEndpointsApiExplorer and AddSwaggerGen. Decorate endpoints with WithName, WithTags, and ProducesResponseType to enrich OpenAPI output. Good docs and integration tests remain essential.
Know When to Use Controllers: If you’re migrating a large app that already uses controllers or needs features like scaffolding and Razor views, you can keep controllers and add minimal endpoints for new functionality. ASP.NET Core lets both coexist. For many new microservices, Minimal APIs hit the sweet spot.
Stay Updated with .NET Releases: Minimal APIs gained features in .NET 7 and .NET 8 (route groups, typed results, form binding, better output caching, AOT readiness). Keep current to benefit from improvements and new patterns.

Conclusion

Minimal APIs in .NET have emerged as a powerful way to build web services with less code and great performance. They strip away the boilerplate of the past, allowing architects and developers to craft endpoints that are explicit, fast, and easy to maintain. We’ve seen how they compare to traditional MVC controllers – trading some built-in conveniences for a more streamlined and efficient model – and why many modern cloud applications and microservices favor this minimal approach. With .NET 8 and beyond, Minimal APIs are maturing with more features, making them suitable for projects of all sizes.

In adopting Minimal APIs, apply sound software engineering practices: organize your code well, leverage dependency injection and middleware wisely, and keep things testable and secure. When done right, a Minimal API-based solution can be highly scalable, performant, and developer-friendly. Whether you’re building a simple CRUD microservice or a high-throughput backend for a mobile app, Minimal APIs offer a compelling toolkit in the ASP.NET Core framework.

In summary, Minimal APIs provide a modern, efficient alternative to controllers – one that aligns with today’s emphasis on microservices, cloud optimization, and rapid development. By understanding their strengths and using the best practices outlined above, you’ll be well-equipped to leverage Minimal APIs for your next .NET project and reap the benefits of their simplicity and speed.

References

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