ILSpy is a cross-platform .NET assembly browser and decompiler that converts compiled .NET code back into readable source form.
The tool addresses the need to understand and analyze compiled .NET assemblies by performing decompilation—the reverse process of compilation. It reads intermediate language bytecode and metadata from .NET assemblies and reconstructs equivalent C# source code. The decompiler supports modern .NET features including ReadyToRun compiled code and can generate PDB debug symbol files to aid in analysis and debugging.
Developers should choose ILSpy when they need to inspect third-party libraries, understand legacy code without source access, or verify what their own compiled code contains. The tool suits anyone working with .NET across Windows, Linux, and macOS through its desktop application built on Avalonia. Beyond the standalone UI, the project provides multiple integration points: a Visual Studio 2022 extension, a Visual Studio Code extension, a command-line dotnet tool, and NuGet packages for embedding decompilation into custom applications. The decompiler engine is also integrated into Visual Studio 2022 and 2026 for F12 navigation support.
The project maintains steady activity with regular updates to support new .NET language features and runtime capabilities. Development includes ongoing refinement of decompilation accuracy and expansion of supported .NET constructs. The tool receives contributions that address edge cases in code reconstruction and improve handling of complex metadata scenarios. Maintenance spans multiple frontend implementations, indicating sustained effort to keep the decompiler accessible across different development environments.
