What is the RESOURCES file format?
Files with the .resources extension contain data used by applications developed in the Microsoft .NET ecosystem, most often within the Visual Studio development environment. .resources files store objects - such as strings, images, icons, and binary data - utilized by the application at runtime.
These are compiled binary files generated automatically from .resx (XML resource) source files by ResGen.exe (the Resource File Generator) during the build process. The binary format is identified by the magic number 0xBEEFCACE at the start of the file. Developers normally edit .resx files in the Visual Studio designer; the .resources file is an intermediate build artifact they rarely touch directly.
Placing application resources in .resources files enables direct references to their contents in source code via the ResourceManager class. For already compiled applications, specialized resource editors can replace original objects - this approach is most commonly used to create program language localizations by substituting original texts with their translated equivalents, without recompiling the entire application.
At runtime, ResourceManager loads the compiled .resources file either embedded in the main assembly or as a satellite assembly (.resources.dll) for a specific locale.
An important caveat for modern .NET development: .resources files that contain complex objects serialized with BinaryFormatter are deprecated as of .NET 5 and blocked by default in .NET 7+ due to security risks. String, image, and primitive-type resources are unaffected. The format has been part of the .NET platform since .NET Framework 1.0 (2002) and remains unchanged through .NET 9 (2024).
Security & safety
RISK: LOW.resources files themselves are data files, not executable. However, they may contain BinaryFormatter-serialized objects (legacy .NET 1-4 style) which, if deserialized, can execute arbitrary code - this is why .NET 7+ disables BinaryFormatter by default. Opening a .resources file in a text editor or ResGen.exe is safe; only deserializing untrusted complex-type resources poses a risk.
Format details
in a nutshellPrograms that open RESOURCES files
Windows3 apps
Microsoft Visual Studio
Freemium Open the source .resx file in Solution Explorer - VS shows a designer grid. The .resources file in obj/ is auto-generated on build and normally not opened directly. 
ResGen.exe (.NET SDK tool)
Free resgen.exe file.resources file.resx - decompiles .resources back to .resx XML. Included with .NET SDK.
dnSpy / ILSpy
Open-source Open the .dll/.exe assembly in dnSpy - resources embedded as .resources are listed under 'Resources' node and can be exported. 
macOS1 app
Visual Studio Code + C# Dev Kit
Open-source Edit source .resx; 'dotnet build' regenerates .resources. 
Linux1 app
Visual Studio Code + C# Dev Kit
Open-source Edit the source .resx file; 'dotnet build' regenerates the .resources binary automatically. Technical details
deep spec| File type | Compiled binary .NET resource file |
| Magic number | `0xBEEFCACE` (4 bytes, little-endian, at offset 0) |
| Header version | ResourceManager.HeaderVersionNumber = 1 (stable since .NET 1.0) |
| Byte order | Little-endian (header integers); resource data encoding varies by type |
| String encoding | UTF-16 LE for resource names; UTF-8 for type names in header |
| Build tool | `ResGen.exe` compiles from .resx XML source; runs automatically during Visual Studio build |
| Runtime loader | `System.Resources.ResourceManager` - embedded in assembly or satellite .resources.dll |
| Typical size | 1 KB - 10 MB (larger with embedded images or audio) |
| Primitive types | 19 primitive types (string, int, bool, etc.) use compact binary encoding |
| BinaryFormatter status | Deprecated .NET 5+; disabled by default in .NET 7+ (arbitrary code execution risk) |
| Introduced | .NET Framework 1.0 (February 2002) |
| Platform support | Windows (.NET Framework), Linux and macOS (.NET Core / .NET 5+) |
| UWP/WinAppSDK replacement | .resw (same XML schema as .resx) compiled to .pri (Package Resource Index) |
| Released | .NET Framework 1.0 (2002) |
| Latest version | .NET 9 (2024) - format unchanged since inception; ResourceManager.HeaderVersionNumber = 1 |
| Specification | learn.microsoft.com |
RESOURCES conversions
Community Q&A
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