Quickly browsing the .NET source code without installing or downloading anything

Sometimes you just want to see how something works inside .NET, without cloning repositories or setting up large source trees. Fortunately, Microsoft now provides an easy way to browse the complete .NET Framework and .NET Core source code directly online.

For .NET Framework, there's the long-running Reference Source website. You can search for any class or method and see the original C# implementation, including comments and links to related symbols.

For .NET Core and newer versions, the best option is source.dot.net. It provides fast, searchable access to the full .NET runtime and library sources and it works entirely in the browser. No need to download anything.

For example, if you ever wondered how StringBuilder or Task classes are implemented, you can just search and inspect the methods directly. The site even shows which NuGet package each class belongs to.

These reference sites are incredibly valuable for learning and debugging. Understanding how Microsoft's own base class libraries are structured can make you a better developer. Also, they often explain the "why" certain APIs behave the way they do.