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Slack formatting guide

Slack Bold and Italic Not Working? Use mrkdwn

If **bold** or __italic__ shows literal symbols in Slack, you are using Markdown instead of mrkdwn. Here is the fix.

Direct answer

Slack bold is a single asterisk (*bold*) and italic is underscores (_italic_). If you typed **bold** or __italic__ from standard Markdown, Slack shows the literal symbols because mrkdwn uses single markers. Replace the double markers with single ones, or convert the Markdown to mrkdwn.

Open Markdown to Slack converter

When to use this

  • Your bold or italic shows asterisks or underscores instead of formatting.
  • You pasted Markdown into Slack and the styling did not apply.
  • A Slack bot or app message is not rendering emphasis.

Steps

  1. Change **bold** to *bold* (one asterisk on each side).
  2. Change __italic__ or *italic* to _italic_ (underscores).
  3. Change ~~strike~~ to ~strike~ (one tilde).
  4. Make sure there is no space between the marker and the text.
  5. For a whole document, convert the Markdown to mrkdwn instead of fixing each mark.

Example conversion

Markdown input
This is **very important** and _slightly_ urgent, not ~~cancelled~~.
Slack mrkdwn output
This is *very important* and _slightly_ urgent, not ~cancelled~.

Common mistakes

  • Double markers are the top cause: **bold** and ~~strike~~ are Markdown, not mrkdwn.
  • A space right after the marker breaks it: * bold * will not format.
  • Bot and Slack app messages need the mrkdwn field set and single-marker syntax to render emphasis.

FAQ

Why is bold not working in Slack?
You are probably using **bold** from standard Markdown. Slack mrkdwn bold is a single asterisk, so use *bold* and the double asterisks will disappear.
How do I italicize text in Slack?
Wrap the text in underscores: _italic_. A single asterisk is bold in Slack, not italic, which trips up people coming from Markdown.
Why do my asterisks show as plain text?
Either you used double asterisks (Markdown bold) or there is a space between the asterisk and the word. Use single markers with no inner spaces.

Related Markdown to Slack guides

Slack Message Formatting Syntax (mrkdwn vs Markdown)

Slack uses mrkdwn, not standard Markdown: one asterisk for bold, underscores for italic, and angle-bracket links. Here is the full reference.

Convert Markdown to Slack mrkdwn

Turn standard Markdown into Slack mrkdwn — bold, italic, strikethrough, links, and headings mapped to Slack's syntax.

How to Post Code Blocks in Slack

Use backticks for inline code and triple backticks for multi-line code blocks in Slack messages, and know what Slack does not support.

Paste Formatted Text Into Slack Without Breaking It

Move text from Markdown, Google Docs, or Notion into Slack cleanly by converting to mrkdwn or clearing carried-over formatting.

How to Make Bullet Points and Lists in Slack

Create bullet points and numbered lists in Slack using the composer's list buttons or literal bullet characters for bot messages.