sln

sln is the Visual Studio Solution File extension, used by Microsoft Visual Studio and compatible IDEs to organize one or more software projects into a single coordinating unit. A solution file, typically named with a .sln extension, serves as a container rather than containing source code itself. It references project files such as .csproj, .vbproj, .vcxproj, and others, enabling coordinated building, debugging, and navigation across multiple projects.

A .sln file is a text-based manifest that includes a header, a list of projects, and a global section with solution-wide settings. Each project entry specifies a project type GUID, the project name, the relative path to the project file, and the project GUID. The global section contains configuration mappings that define how each project should be built in different configurations and platforms, such as Debug or Release on various CPU targets. It may also indicate the startup project and project dependencies within the solution.

The primary purpose of a solution is to provide a convenient workspace for working with related projects. It does not perform compilation itself; instead, it orchestrates the build process by coordinating the individual project files and the underlying build system (for example, MSBuild on Windows). This arrangement allows developers to manage multi-project configurations, shared settings, and dependencies from a single place, while still benefiting from each project’s specific tooling and build rules.

Although most commonly edited and used with Visual Studio, .sln files can be opened by other IDEs that support Visual Studio project formats, such as JetBrains Rider or Visual Studio for Mac. Some editors or command-line workflows may recreate or regenerate solutions, and manual edits to a .sln file are possible but should be performed with care to preserve GUIDs and formatting.