What is MIME type "text/x-lean4"?

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-lean4 tags files that contain Lean 4 code. It tells programs the file is plain text but uses special syntax for formal proofs and programming.

This MIME type is custom. The x- prefix signals experimental or non-standard usage. Tools like code editors and IDEs use it to load proper syntax highlighting, error checking, and auto-completion features when working with Lean 4 files.

Main use: It identifies source code written in the Lean 4 language.
Additional uses: Supports integration in development environments for theorem proving and formal verification.
Key fact: It marks the file as human-readable plain text with domain-specific formatting.

Files with this MIME type are typically saved with the LEAN extension.

For more technical details on Lean 4, visit the Lean project website.

Associated file extensions

.lean

Usage Examples

HTTP Header

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


    Content-Type: text/x-lean4

HTML

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


    <a href="file.dat" type="text/x-lean4">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-lean4');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.lean

FAQs

What is the text/x-lean4 MIME type used for?

The MIME type text/x-lean4 specifically identifies source code files written for the Lean 4 theorem prover and programming language. It is used by web servers and IDEs to distinguish Lean 4 code from generic text or older versions of the language, ensuring that files with the .lean extension are processed correctly.

How do I configure Apache to serve Lean 4 files correctly?

To serve Lean files with the correct MIME type on an Apache server, add the following line to your .htaccess file or main configuration. This ensures browsers and client applications recognize the file format:

AddType text/x-lean4 .lean

How do I add text/x-lean4 support to Nginx?

For Nginx, you need to update your mime.types file or include a types block inside your server configuration. Use the following directive to map the extension:

types { text/x-lean4 lean; }

Why does this MIME type have an 'x-' prefix?

The x- prefix in text/x-lean4 indicates that it is a non-standard or experimental subtype not yet officially registered with the IANA. While it is not a standard type like text/html, it is the convention used by the community and tools to identify Lean 4 specific syntax.

Which software opens files with the text/x-lean4 content type?

These files are best opened using Visual Studio Code (VS Code) with the official Lean 4 extension installed. While any text editor (like Notepad or Vim) can open the file because it is plain text, dedicated tools provide essential features like live error checking and mathematical symbol rendering.

Why do special characters look strange when I view a Lean 4 file in a browser?

Lean 4 code heavily utilizes Unicode characters for mathematical notation. If your web server does not send the correct character encoding header (e.g., Content-Type: text/x-lean4; charset=utf-8), browsers may display these symbols as garbled text or "mojibake."

Are text/x-lean4 files safe to download?

Generally, yes, as they are plain text source code files. However, because they contain programming logic, you should treat them as executable code. Do not compile or run Lean 4 files from untrusted sources, as they could theoretically execute malicious commands on your machine during the build process.

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.