Understanding Filters in Minimal API with .NET 9.0

When Minimal APIs came out in .NET 6, they quickly became popular for building fast and lightweight web services. However, earlier versions didn’t have a good way to handle common tasks like validation, logging, or authorization without repeating the same code.

That’s where Endpoint Filters come in — first introduced in .NET 7, improved in .NET 8, and now even better in .NET 9 with easier usage, grouping options, and more control over the request pipeline.

In this post, we’ll look at Filters in Minimal APIs with .NET 9 — how they work and how you can use them effectively with modern best practices.