What is the CSPROJ file format?
Files with the .csproj extension are C# project files belonging to the developer files category.
What do .csproj files contain?
The content of .csproj files includes build settings for projects written in C#. They are generated by Microsoft Visual Studio or the .NET SDK command-line tools when a new project is created. The following information can be found in .csproj files:
- project name and output type (executable or class library),
- references to project files, NuGet package dependencies (
<PackageReference>), and other project references, - compilation parameters and target framework (e.g.
net9.0ornet48), - assembly metadata such as version numbers and author information.
The content of .csproj files is written using XML markup. Modern projects use the compact SDK-style format, introduced with .NET Core and Visual Studio 2017, which opens with <Project Sdk="Microsoft.NET.Sdk"> and is typically just a few lines long - source .cs files are picked up automatically via implicit globbing. Older legacy projects (pre-2017) use a more verbose format with an explicit xmlns="http://schemas.microsoft.com/developer/msbuild/2003" namespace declaration and list every source file individually.
What are .csproj files used for?
With .csproj files, one can store all build parameters of often very complex projects - which may consist of several hundred source files and external dependencies - in a single document. The build engine MSBuild (or the dotnet build CLI command) reads .csproj to compile the project. Information in .csproj files also ensures consistent behavior across different machines and CI environments, eliminating the need to supply compilation parameters each time. One or more .csproj projects are grouped together by a solution file (.sln or the newer .slnx).
Note that .csproj itself holds no source code - all C# code resides in the separate .cs files it references.
Can I open .csproj files?
.csproj files are automatically generated after selecting the option to create a new project. Because they are written using XML, even the simplest text editor such as Notepad suffices for viewing or editing them. However, it is worth remembering that XML syntax can be unforgiving - without a clear necessity, modifications of .csproj files are discouraged. Rash changes to their content may lead to inconsistencies among project elements, resulting in problems opening the project in Visual Studio or other development tools.
Security & safety
RISK: MEDIUMThe .csproj file itself is plain XML and harmless to read. The real risk is what happens when you BUILD or RESTORE it: a C# project can run MSBuild targets, pre/post-build scripts, NuGet package restore (which can execute install scripts), source generators and the compiled code on debug/run - so opening an untrusted project and pressing Build/Run can execute arbitrary code. Visual Studio shows a trust prompt for downloaded projects for exactly this reason. Inspect an unfamiliar .csproj's targets, package references and scripts before building, and don't build code you don't trust.
Format details
in a nutshellPrograms that open CSPROJ files
Windows4 apps
Microsoft Visual Studio
Freemium Double-click the .csproj (or its .sln) to load the project; the free Community edition builds and runs it. Best full IDE experience for C#. 
Visual Studio Code (with C# Dev Kit)
Free Open the folder containing the .csproj; the C# Dev Kit extension detects and loads the project for editing, building and debugging.
.NET SDK (dotnet CLI)
Free Build/run from a terminal: 'dotnet build MyProject.csproj' or 'dotnet run'. No IDE needed; cross-platform.
Notepad / any text editor
Open-source Open the .csproj as XML to read or hand-edit references, target framework and build settings (no build). 
macOS2 apps
Visual Studio Code (with C# Dev Kit)
Free Open the project folder and add the C# Dev Kit. The standard free way on Mac since Visual Studio for Mac was retired (Aug 2024).
JetBrains Rider
Freemium Open the .csproj/.sln directly; full C# project support on macOS. Free for non-commercial use. 
Linux2 apps
Visual Studio Code (with C# Dev Kit)
Free Open the folder, install the C# Dev Kit plus the .NET SDK to edit, build and debug the project. Technical details
deep spec| File structure | XML with a <Project> root element containing <PropertyGroup>, <ItemGroup>, and optionally <Target> child elements |
| Project format flavors | SDK-style (since .NET Core / VS 2017): compact, uses Sdk attribute and implicit *.cs globbing. Legacy full-framework: verbose, lists every source file explicitly, xmlns 2003 schema |
| SDK attribute | <Project Sdk="Microsoft.NET.Sdk"> opens every modern SDK-style project; variants include Microsoft.NET.Sdk.Web (ASP.NET Core) and Microsoft.NET.Sdk.Worker |
| Target framework declaration | <TargetFramework> element specifies the compile target (e.g. net9.0, net48, netstandard2.0); <TargetFrameworks> (semicolon-separated) enables multi-targeting in one file |
| NuGet dependency declaration | <PackageReference Include="PackageName" Version="x.y.z" /> elements inside an <ItemGroup>; replaces the older packages.config approach |
| Project-to-project references | <ProjectReference Include="../Other/Other.csproj" /> elements; MSBuild resolves build order and dependency graph automatically |
| Source file inclusion (SDK-style) | Implicit - all *.cs files under the project directory are compiled automatically without explicit <Compile> entries |
| Output types | Exe (console application), WinExe (Windows GUI), Library (class library or NuGet package); set via the <OutputType> property |
| Build engine | MSBuild - invoked directly or via dotnet build, dotnet run, and dotnet publish from the .NET SDK CLI |
| Text encoding | UTF-8 plain text; no binary signature or magic bytes; BOM is optional and omitted in most modern tooling |
| Typical file size | Under 1 KB for SDK-style projects; up to ~50 KB for large legacy full-framework projects with many explicit file entries |
| MIME type | application/xml (also accepted as text/xml or text/plain) |
| Companion file | .csproj.user stores per-user, machine-local IDE settings (e.g. debug launch arguments) and should not be committed to version control |
| Solution grouping | One or more .csproj projects are combined into a .sln or the newer .slnx solution file for IDE and multi-project CLI builds |
| Counterpart project formats | .vbproj (Visual Basic .NET) and .fsproj (F#) use the same MSBuild XML schema and can coexist in the same solution |
| Released | 2002 (Visual Studio .NET / .NET Framework 1.0) |
| Latest version | SDK-style project format (since .NET Core / VS 2017, 2017); current with .NET 9 (2024) |
| Open standard | Yes · royalty-free |
| Specification | learn.microsoft.com |
CSPROJ conversions
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