What is MIME type "text/x-csharp"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

The MIME type text/x-csharp marks files as containing C# code. It tells software that the text follows the syntax and rules of the C# language.
This helps code editors and compilers apply the right syntax highlighting and formatting.

Files with this MIME type are used in several ways:

Providing standard CS source files for C# projects.
Enabling script execution in files like CSX.
Supporting build automation with CAKE files that use C# syntax.
Handling specialized or preprocessed code in files such as CS.PP.
Accommodating less common variants like BF, EQ, LINQ, and UNO that follow similar code rules.

This non-standard label (with the x- prefix) means it isn’t officially registered but is commonly used among developers. It ensures that files containing C# code are recognized by various development tools and environments.

Associated file extensions

.cs, .bf, .csx, .cake, .cs.pp, .eq, .linq, .uno

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: text/x-csharp

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="text/x-csharp">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');    
    
    http.createServer((req, res) => {    
      res.setHeader('Content-Type', 'text/x-csharp');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.cs, .bf, .csx, .cake, .cs.pp, .eq, .linq, .uno

FAQs

How do I configure Apache to serve C# files with the correct MIME type?

To ensure your Apache server serves .cs files as C# code, add the following line to your .htaccess file or main configuration: AddType text/x-csharp .cs .csx. This ensures browsers and tools identify the content as C# source code rather than generic text.

What is the Nginx configuration for text/x-csharp?

In Nginx, you can map file extensions to this MIME type within your mime.types file or the types block in nginx.conf. Add the line: text/x-csharp cs csx;. After saving, reload Nginx to apply the changes.

Is text/x-csharp a standard IANA MIME type?

No, the x- prefix indicates that text/x-csharp is a non-standard or experimental type not officially registered with IANA. However, it is the de facto standard used by developers and web servers to distinguish C# code from plain text.

Can web browsers execute files served as text/x-csharp?

No, web browsers do not natively execute C# source code. When a browser encounters a file with this MIME type, it will typically display the code as text, often useful for documentation or code sharing. To run C# in a browser, technologies like WebAssembly (Blazor) are required, which typically use compiled .dll or .wasm files, not raw .cs source.

Why should I use text/x-csharp instead of text/plain?

While text/plain will display the content correctly, using text/x-csharp provides semantic meaning to the file. This allows sophisticated text editors, browser extensions, and IDEs to automatically apply syntax highlighting and formatting specific to the C# language.

What is the difference between .cs and .csx files using this MIME type?

Standard .cs files contain compiled C# code definitions (classes, namespaces) used in building applications. In contrast, .csx files are C# Scripts designed to be executed directly by scripting engines like Roslyn or standard tools like dotnet-script without a full compilation step.

Why does my browser download .cs files instead of displaying them?

This usually happens if the server sends the Content-Disposition: attachment header or if the MIME type is set to application/octet-stream. To fix this, ensure the server sends the text/x-csharp (or text/plain) header and set the Content-Disposition to inline.

General FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.