What is MIME type "image/cis-cod"?

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

image/cis-cod identifies files that use the Lightning Strike image format. It tells systems that the file’s data is stored in a unique, specialized format.
Files with this MIME type are typically saved with the COD extension. Applications use this information to select the correct decoder and renderer.

Main Use: Displaying images in software built specifically for the Lightning Strike format.
Key Fact: It uses a distinct method for compressing and rendering image data.
Usage: Found in niche or legacy systems that rely on specialized image handling.
Purpose: Instructs browsers and file handlers to process the image correctly.

For more details on MIME types, visit the IANA Media Types page.

Associated file extensions

.cod

Usage Examples

HTTP Header

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


    Content-Type: image/cis-cod

HTML

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


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

Associated file extensions

.cod

FAQs

Do modern web browsers support image/cis-cod?

No, modern browsers like Chrome, Firefox, and Edge do not natively support the image/cis-cod MIME type or the Lightning Strike format. To ensure images are visible to all users, it is highly recommended to convert these files to standard types like image/jpeg or image/png.

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

Files associated with image/cis-cod require specialized image viewers such as XnView, IrfanView (often requiring a plugin), or legacy CompuServe software. Standard operating system photo viewers usually cannot decode the Lightning Strike compression algorithm used in these files.

How do I configure Apache to serve .cod files correctly?

To serve these files with the correct MIME type, add the following line to your .htaccess file or httpd.conf: AddType image/cis-cod .cod. This ensures the server tells the client that the file is a CIS COD image rather than a generic binary stream.

Is every .cod file an image?

No, the .cod extension is ambiguous and is sometimes used for compiled source code, Fortran files, or other data types. The MIME type image/cis-cod specifically identifies the file as a raster image, distinguishing it from code or text files that might share the same extension.

Why does the browser download the .cod file instead of displaying it?

When a browser encounters a MIME type it cannot render, such as image/cis-cod, its default behavior is to download the file to the user's computer. This confirms the server is sending the correct headers, but the client application lacks the necessary decoder to show the image inline.

What is the Lightning Strike format?

Lightning Strike is a proprietary wavelet-based image compression technology developed by Infinity for CompuServe (CIS). While it offered high compression ratios in the 1990s, it is now considered a legacy format and is rarely used in modern web development.

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.