What is MIME type "image/x-sgi-bw"?

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

The MIME type image/x-sgi-bw is a legacy format from Silicon Graphics.
It defines images stored as raw, single-bit data—essentially black and white. When an application sees this type, it knows to process the image with this specific, simple structure.
Files using this type usually come as RGB or BW images.

Main use case: Handling non-colored, binary images.
Legacy systems: Originally common on Silicon Graphics workstations.
Technical note: Its simple structure may require conversion for modern applications.
Other uses: Useful in specialized graphics projects where simplicity and low storage are valued.

For further details, check the Silicon Graphics Image description.

Associated file extensions

.rgb, .bw

Usage Examples

HTTP Header

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


    Content-Type: image/x-sgi-bw

HTML

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


    <a href="file.dat" type="image/x-sgi-bw">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', 'image/x-sgi-bw');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.rgb, .bw

FAQs

Can modern web browsers display image/x-sgi-bw files directly?

No, modern browsers like Chrome, Firefox, and Edge do not natively support SGI image formats. To display these images on a website, you must convert them to standard web formats like image/png or image/jpeg.

How do I open a file with the .bw extension?

You usually need specialized image editing software or legacy viewers to open files served as image/x-sgi-bw. Tools like GIMP, XnView, and IrfanView can typically read Silicon Graphics image data, whereas standard Windows or Mac photo viewers will likely fail.

How do I configure Apache to serve SGI BW files correctly?

To ensure your Apache server sends the correct headers for these files, add the MIME mapping to your .htaccess file or main configuration. Use the directive: AddType image/x-sgi-bw .bw .rgb.

What does the 'x-' prefix indicate in image/x-sgi-bw?

The x- prefix signifies that this is a non-standard or proprietary MIME type not originally registered with the IANA standards body. It specifically identifies a format developed by Silicon Graphics for their workstations, distinguishing it from standard types.

How can I convert SGI BW images to PNG using the command line?

The tool ImageMagick is the industry standard for converting legacy formats like this. You can run the command convert filename.bw filename.png to transform the raw SGI black-and-white data into a modern, compatible image.

Why are .rgb files sometimes associated with this black-and-white MIME type?

In legacy Silicon Graphics environments, the extensions .rgb, .sgi, and .bw were sometimes used interchangeably depending on the specific system configuration. While image/x-sgi-bw specifically denotes monochrome data, the file might still carry a generic SGI extension like .rgb.

What is the correct Nginx configuration for this MIME type?

For Nginx, you should update your mime.types file or add a types block within your server configuration. Add the line image/x-sgi-bw bw rgb; to ensure the server correctly identifies both .bw and .rgb files as SGI images.

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.