No, in fact, Slack doesn’t support Markdown in messages¹ at all. It uses its own similar-at-a-glance format called mrkdwn which has some notable differences with Markdown:
- In Markdown, both
*and_are used for emphasis - In Markdown, both
**and__are used for bold - In
mrkdwn*is used for bold and_is used for emphasis - Markdown has no syntax for strikethrough (though some implementations have added it, e.g. in GFM which uses
~~) butmrkdwnuses~for strikethrough - Link syntax is very different
mrkdwndoesn’t support headings- Probably more
Don’t expect arbitrary Markdown² to work in Slack messages.
¹Slack does support Markdown in posts which can be created using the files.upload API endpoint setting filetype to post.
²Note that tables aren’t supported in regular Markdown either. Like strikethrough, some implementations have added these.