In my experience (using lots of different Markdown-related tools), .md is the most common extension, with .markdown a distant second. The rest of them (.mdown, .mkdn or whatever) I’ve never encountered in the wild (but some of the editors I’ve used support them).
.mark sounds good, though .md is used more often. If commonmark is highly compatible with gruber’s markdown, just stick to .md, if not then try .mark.
Btw, just notice that R statistic program name their fancy styled markdown document as .rmd to indicate that it is a markdown formatted document that has inline executable R snippets.
Whatever extension you choose like .md or .mark, I recommend adding a ‘Recommendation’ for filenames like .R.mark for R or .py.mark for python. So at least the file can be read even if there is no python or R hooks in the CommomMark reader.
For any file claiming to contain Markdown, the .markdown extension is the most readable and logical. The .md extension is most widely used. All other variations (.mdown, .mkdn, .markdn) are neither readable nor widely used, and as there are 49 ways of arranging the letters of the word into an extension, we should ignore those all.
However, to call CommonMark Markdown would be similar to calling LESS and SASS CSS. Yes, the original subset is still supported in the new language, but the new language is so much more.
Unless CommonMark’s development halts today, it will be a very different beast next year. It will support syntaxes and extensions that have never been valid Markdown. Just like how CommonMark has a name that’s distinct from Markdown, I support giving it an extension and MIME-type distinct from Markdown, and I like Sanpi’s proposed.mark extension.
I realize .md is the most common extension, however it’s also used by GCC machine description files and Modula. Vim, for example, only recognizes .md as Markdown in README.md by default [source]. The second most widely supported extension is .markdown. Other extensions are not supported everywhere (for example, the second shortest .mkd is not supported by Bitbucket) and I find them unreadable anyway.
Conclusion: In my opinion, .markdown should be the officially endorsed standard, but tools should probably also support at least .md where feasible.
Syntax highlighters need either an extension or a hashbang, else they have to resort to more complicated heuristics.
A common convention on Unix/Linux systems is for executable files to have a hashbang and no extension, and for libraries to have an extension (.pl, .py, .rb, etc.) and no hashbang.
You can’t really have extensionless files on Windows; for example, README will be recognized as a README file.
Therefore, Markdown certainly does need an extension. Now, I’m not saying there should be just “one true extension”, but a standard would be certainly nice—one that makes sense, i.e. not something like .text.
Is it possible to also use the ‘naturalization argument’? That the majority of markdown files out there in the wild is already named “.md”, so any files we read should be in “.md” (if we are strictly compatible with majority of markdown formatted files).
If we are not strictly compatible with majority of markdown files, then we should use .cm or .mark, or .mk. Thought an argument can be made that .md is a generic file extension for lightly marked up text, and thus is not markdown specific.
That might be the way to go and we could also to look at the extension apps save Markdown files in. I personally use iA Writer for Mac which saves files with the .md extension by default (but recognises other extensions like .markdown). We could do a comparison of apps which read and write Markdown files and list what file extensions are used.
It’s a poor metric because without the file being present, Github tells you to create a file called README.md. Not a file called README.md or README.markdown.
If you don’t see that as a black mark big enough to make the metric useless, I’m honestly not sure how why we’d continue this conversation.
In standardizing a thing explicitly not to be standardized, a new thing is created. That appears to be recognized, as a new name was picked. A new extension should be picked as well.
It does not prevent Markdown from being processed by Commonmark. It prevents Commonmark from being processed by Markdown.
The half in/half our nature of this project will be its undoing. I’ve already lost most of my interest in the project as a whole over this thread.
“.md is better because it is shorter I don’t want file names to take my whole screen in width”
We’re not living in the world of 8.3 file names for a long time now. The same argument could be applied to .torrent as well, which is only one character shorter than .markdown. Short extensions can be nice but .md is already ambiguous even without Markdown.
For what it’s worth, it seems as of revision 6292, Vim recognizes all .md files as Markdown (not counting possible ftdetect magic). The first release that includes this is Vim 7.4.480 (based on revision 6293).
$ hg blame runtime/filetype.vim | grep -i markdown
[...]
6292: au BufNewFile,BufRead *.markdown,*.mdown,*.mkd,*.mkdn,*.mdwn,*.md setf markdown
6292: " Modula 2 (.md removed in favor of Markdown)
[...]