SLN file format: lines and sections

Microsoft’s documentation describes the header and the loading process; the details of the sections are taken from Microsoft’s two open-source readers of the format: MSBuild’s SolutionFile.cs and the vs-solutionpersistence library. A solution keeps shared state; per-user options go in a separate binary .suo file.

Header

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.2.32505.173
MinimumVisualStudioVersion = 10.0.40219.1

The header from Microsoft’s documentation.

Line	Meaning
`Microsoft Visual Studio Solution File, Format Version 12.00`	The format version; 12.00 is current. MSBuild looks for it in the first two lines, rejects versions below 7 and only notes versions above the newest it knows.
`# Visual Studio Version 17`	Major version of the Visual Studio that last saved the file; it sets the version shown on the solution’s icon.
`VisualStudioVersion = …`	Full version of the Visual Studio that saved it (not updated by later saves from the same major version).
`MinimumVisualStudioVersion = …`	Oldest Visual Studio that can open the solution.

Project lines

Project("{type GUID}") = "name", "path", "{project GUID}"
	ProjectSection(name) = preProject|postProject
		key = value
	EndProjectSection
EndProject

Field	Meaning
`type GUID`	The kind of project, which selects the Visual Studio package that loads it (table below).
`name`	The project’s name in the solution.
`path`	The project file, ideally relative to the solution file.
`project GUID`	The project’s own ID, used by the global sections.

Project sections

Section	Contents
`ProjectDependencies`	The project’s build dependencies: one `key = value` line per dependency, whose key is the other project’s GUID.
`SolutionItems`	A solution folder’s files.
`WebsiteProperties`	Settings of a web site project, keyed `configuration.name` (e.g. `AspNetCompiler.VirtualPath`), plus `ProjectReferences` and `TargetFrameworkMoniker`.

Project type GUIDs

The types vs-solutionpersistence knows:

Type GUID	Project	Extension
`FAE04EC0-301F-11D3-BF4B-00C04F79EFBC`	C#	`.csproj`
`9A19103F-16F7-4668-BE54-9A1E7A4F7556`	C# (common project system)	–
`F184B08F-C81C-45F6-A57F-5ABD9991F28F`	Visual Basic	`.vbproj`
`778DAE3C-4631-46EA-AA77-85C1314464D9`	Visual Basic (common project system)	–
`F2A71F9B-5D33-465A-A702-920D77279786`	F#	`.fsproj`
`6EC3EE1D-3C4E-46DD-8F32-0CC8E7565705`	F# (common project system)	–
`8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942`	C++	`.vcxproj`, `.vcxitems`
`D954291E-2A0B-460D-934E-DC6B0785DB48`	Shared project	`.shproj`
`2150E333-8FDC-42A3-9474-1A3956D46DE8`	Solution folder	–
`E24C65DC-7377-472B-9ABA-BC803B73C61A`	Web site	`.webproj`
`911E67C6-3D85-4FCE-B560-20A9C3E3FF48`	Executable	`.exe`
`54A90642-561A-4BB1-A94E-469ADEE60C69`	JavaScript	`.esproj`
`9092AA53-FB77-4645-B42D-1CCCA6BD08BD`	Node.js	`.njsproj`
`151D2E53-A2C4-4D7D-83FE-D05416EBD58E`	Deployment	`.deployproj`
`54435603-DBB4-11D2-8724-00A0C9A8B90C`	Installer	`.vsproj`
`930C7802-8A8C-48F9-8165-68863BCCD9DD`	WiX	`.wixproj`
`00D1A9C2-B5F0-4AF3-8072-F6C62B433612`	SQL database	`.sqlproj`
`0C603C2C-620A-423B-A800-4F3E2F6281F1`	U-SQL database	`.usqldbproj`
`182E2583-ECAD-465B-BB50-91101D7C24CE`	U-SQL	`.usqlproj`
`F14B399A-7131-4C87-9E4B-1186C45EF12D`	Reporting Services	`.rptproj`
`A07B5EB6-E848-4116-A8D0-A826331D98C6`	Service Fabric	`.sfproj`
`CC5FD16D-436D-48AD-A40C-5A424C6E3E79`	Cloud computing	`.ccproj`
`E53339B2-1760-4266-BCC7-CA923CBCF16C`	Docker	`.dcproj`

Other packages register further GUIDs; there is no complete public list.

Global sections

Global
	GlobalSection(name) = preSolution|postSolution
		key = value
	EndGlobalSection
EndGlobal

When a solution opens, Visual Studio first processes the preSolution sections, then the projects, then the postSolution sections. Each section name maps (through the registry) to the package that reads it.

Section	Lines	Meaning
`SolutionConfigurationPlatforms`	`Debug\|Any CPU = Debug\|Any CPU`	The solution’s configurations; both sides are the same `configuration\|platform`. A `DESCRIPTION` entry is ignored by MSBuild.
`ProjectConfigurationPlatforms`	`{project}.config\|platform.ActiveCfg = config\|platform`	Which project configuration each solution configuration uses. A matching `.Build.0` line means the project is built in it (no line: not built); a `.Deploy.0` line also exists (named for deployment; not read by MSBuild’s older parser).
`SolutionProperties`	`HideSolutionNode = …`	Solution properties, such as `HideSolutionNode`.
`NestedProjects`	`{child} = {parent}`	Gives a project its parent (a solution folder).
`ExtensibilityGlobals`	`SolutionGuid = {…}`	Solution-wide values for extensions, such as the solution’s GUID.
`SharedMSBuildProjectFiles`	–	Shared project system properties.
`SolutionConfiguration`, `ProjectConfiguration`, `ProjectDependencies`, `SolutionNotes`, `ExtensibilityAddIns`	e.g. `ConfigName.0 = Debug`	Older sections shown in Microsoft’s documentation example (configurations without platforms, add-ins, notes).

Packages can store their own sections, which Visual Studio reads and writes through IVsPersistSolutionProps.

Example

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.2.32505.173
MinimumVisualStudioVersion = 10.0.40219.1
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "App", "src\App\App.csproj", "{8CDD8387-B905-44A8-B5D5-07BB50E05BEA}"
EndProject
Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{5D2A0E11-0000-4000-8000-000000000001}"
EndProject
Global
	GlobalSection(SolutionConfigurationPlatforms) = preSolution
		Debug|Any CPU = Debug|Any CPU
		Release|Any CPU = Release|Any CPU
	EndGlobalSection
	GlobalSection(ProjectConfigurationPlatforms) = postSolution
		{8CDD8387-B905-44A8-B5D5-07BB50E05BEA}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
		{8CDD8387-B905-44A8-B5D5-07BB50E05BEA}.Debug|Any CPU.Build.0 = Debug|Any CPU
		{8CDD8387-B905-44A8-B5D5-07BB50E05BEA}.Release|Any CPU.ActiveCfg = Release|Any CPU
		{8CDD8387-B905-44A8-B5D5-07BB50E05BEA}.Release|Any CPU.Build.0 = Release|Any CPU
	EndGlobalSection
	GlobalSection(NestedProjects) = preSolution
		{8CDD8387-B905-44A8-B5D5-07BB50E05BEA} = {5D2A0E11-0000-4000-8000-000000000001}
	EndGlobalSection
EndGlobal

An illustration of a C# project inside a solution folder, put together from the forms above (the folder GUID and the pre/post placements are illustrative).

Sources

Microsoft Learn, Project solution (.sln) file (header lines, loading order, the example sections, the .suo file). MSBuild source src/Build/Construction/Solution/SolutionFile.cs (header search and version limits, Project line pattern, configuration lines, .Build.0, nested projects, project dependencies, web site properties). vs-solutionpersistence source SlnConstants.cs, SectionName.cs and ProjectTypeTable.BuiltInTypes.cs (keywords, section names, HideSolutionNode, SolutionGuid, project types). Whether each modern section is written preSolution or postSolution is not stated in these sources and is left out.

.SLN File Format – Lines and sections