Slack calls its formatting syntax “mrkdwn”, and while it looks like Markdown at a glance, it differs in ways that catch almost everyone out. If you’ve ever typed **bold** in Slack and watched the asterisks show up literally, this guide is for you. And if you’d rather preview your message the Slack way before sending, the Slack Markdown formatter renders it live in a Slack-styled view.
Bold — One Asterisk, Not Two
This is the difference that trips up everyone coming from GitHub or standard Markdown. Slack bold uses a single asterisk on each side:
*bold text*Typing **bold** will literally show the extra asterisks. If your bold looks wrong in Slack, this is almost always why.
Italic
Italic uses underscores:
_italic text_Strikethrough — One Tilde, Not Two
Just like bold, strikethrough is a single character. Slack uses one tilde on each side, not two:
~struck through~Inline Code and Code Blocks
Backticks work the same as standard Markdown:
Here's some `inline code`.
```
a fenced code block
keeps its spacing
```Code blocks are especially useful in Slack because they preserve alignment — handy for sharing logs, config, or makeshift tables.
Blockquotes
A > at the start of a line creates a quote:
> This is a quoted lineLinks
Slack uses an angle-bracket format that’s unlike standard Markdown. The URL comes first, then a pipe, then the display text:
<https://markdownmonk.com|Markdown Monk>If you just paste a plain URL, Slack auto-links it — but the angle-bracket format lets you give the link readable text.
Lists
Bulleted and numbered lists both work:
- First item
- Second item
1. Step one
2. Step twoWhat Slack Doesn’t Support
Classic mrkdwn is deliberately minimal:
- No headings.
# Headingrenders as literal text. Use bold to emphasize a line instead. - No underline. There’s no underline syntax in Slack.
- No tables. Use a code block to keep columns aligned.
Standard Markdown vs. Slack mrkdwn
| Format | Standard Markdown | Slack mrkdwn |
|---|---|---|
| Bold | **text** | *text* |
| Italic | *text* or _text_ | _text_ |
| Strikethrough | ~~text~~ | ~text~ |
| Link | [text](url) | <url|text> |
| Heading | # text | not supported |
Preview It the Slack Way
Because Slack’s syntax diverges from standard Markdown, the safest way to format an important message is to preview it first. Paste your text into the Slack Markdown formatter to see it rendered exactly as Slack will display it — single-asterisk bold, single-tilde strikethrough, and all — then copy it into your channel.