The .NET platform (pronounced as "dot net") is a free and open-source, managed computer software framework for Windows, Linux, and macOS operating systems.

At the heart of the .NET Platform is the .NET Framework, a high-productivity, multilanguage development and execution environment for building and running Web services with important features such as cross-language inheritance and debugging.

The company continued development and support of its own implementation as proprietary, closed source software in the meantime.

On November 12, 2014, Microsoft introduced .NET Core—an open-source, cross-platform[6] successor[7] to .NET Framework—and released source code for the .NET Core CoreCLR implementation, source for the "entire [...] library stack" for .NET Core,[8] and announced the adoption of a conventional ("bazaar"-like) open-source development model under the stewardship of the .NET Foundation.

Landwerth acknowledged the disadvantages of the formerly selected shared license, explaining that it made codename Rotor "a non-starter" as a community-developed open source project because it did not meet the criteria of an Open Source Initiative (OSI) approved license.

[19] NET Core 3 adds support for Windows desktop application development[20] and significant performance improvements throughout the base library.

Microsoft initially announced that .NET Core 3 would include the Visual Basic Runtime, but after two years the timeline for such support was updated to .NET 5.

[47] The .NET command-line interface offers an execution entry point for operating systems and provides developer services like compilation and package management.

The dotnet bot served as the placeholder developer for the initial check-in of the .NET source code when it was open-sourced.