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

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

text/x-dockerfile designates plain text files that contain instructions for building container images. These files guide container engines in assembling images step by step.

Primary Functionality:

Main use: Acts as a build blueprint. Commands like FROM, RUN, and COPY direct container creation.
Editor support: Enables syntax highlighting and linting in text editors and IDEs.
Integration: Helps container tools recognize and process build instructions automatically.

Files using this MIME type are typically named without a file extension but are known by convention. For example, one common name is DOCKERFILE and an alternative is DOCKERFILE (often referred to as a containerfile).

For further details, visit the Dockerfile Reference.

Associated file extensions

.dockerfile, .containerfile

Usage Examples

HTTP Header

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


    Content-Type: text/x-dockerfile

HTML

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


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

Associated file extensions

.dockerfile, .containerfile

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.