What is a .mdc file?

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I did a bit of digging for this, because the docs don’t talk about the file format. This is what I was able to confirm:

  1. File format

    Cursor engineer Michael Feldstein (@msfeldstein) mentioned on Twitter that it’s only a Markdown file with structure:

    It’s just a markdown file with structured frontmatter that we render a custom editor for so you can @-mention files in your codebase and to make sure the metadata stays intact.

    Tweet: https://x.com/msfeldstein/status/1884805975556985051

  2. File extension

    Michael also mentioned that the “MDC” in the .mdc file extension means “Markdown Cursor”:

    It means “Markdown Cursor” we just needed a unique extension so we could use the custom editor for these but not for regular markdown files.

    GitHub comment: docs: updated readme and add overviews by bgrenon · Pull Request #1 · neondatabase-labs/ai-rules · GitHub

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