How to Bold Text in Slack (and Italic, Bold Italic)

To bold text in Slack, select the words in the message box and press Cmd+B on a Mac or Ctrl+B on Windows and Linux, or click Bold in the formatting toolbar. You can also type one asterisk on each side of the text, *like this*, with no spaces inside. Typed **bold** with two asterisks also turns into clean bold in the message box. Two asterisks fail when you paste the text, when a bot sends it, and with Format messages with markup on, where the bold keeps a stray asterisk on each side. For italics, press Cmd+I (Ctrl+I) or wrap the text in underscores, _like this_.

The syntax is from Slack's help article "Format your messages in Slack with markup" and the shortcuts from Slack's keyboard shortcuts page, both checked on 27 September. We tested typed, pasted, markup-mode and bot messages in a real Slack workspace on 28 September and repeated the typed and API tests on 5 October.

The message box above, on 5 October 2026: *one asterisk* and **two asterisks** typed at normal speed both turned bold as we typed, Cmd+B made bold, and * spaced * stayed literal. After sending, Slack stored that message with single asterisks (*two asterisks*), so the double version is only a typing shortcut.

Slack text formatting cheat sheet

With the formatting toolbar on (the default), typed markers turn into formatting as you type, so you see the bold before you send. Underline is the one style with no typed marker: use Cmd+U on a Mac, or the toolbar button; see how to underline in Slack.

How to bold text in Slack

• Type your message.
• Double-click a word, or drag across the words you want in bold.
• Press Cmd+B (Mac) or Ctrl+B (Windows, Linux), or click B in the formatting toolbar.
• Press the shortcut again with the text selected to remove the bold.

To bold as you type, press Cmd+B, type the words, and press Cmd+B again to stop. Or type *, the words, and a closing *. The closing asterisk has to touch the last letter.

How to italicize and bold italic in Slack

For italics, select the text and press Cmd+I (Ctrl+I), or wrap it in underscores: _text_. Asterisks do not make italics in Slack; one asterisk is bold.

For bold italic, apply both: select the text and press Cmd+B and then Cmd+I, or type *_text_*. The order of the markers does not matter as long as they nest, so _*text*_ works too.

Slack bold not working? The five usual causes

One timing quirk from our test: when a script typed **two asterisks** with no pause between keys, the box kept a stray * on each side of the bold. Typed at about 8 keys a second it came out clean. If you type very fast or use a text expander, use one asterisk.

You pasted two asterisks. Typed **bold** becomes bold, but pasted **bold** from ChatGPT, GitHub or a doc stays literal. Pressing Cmd+Shift+F (Apply formatting) on it, or clicking Apply formatting in the toast Slack shows, makes it bold with a stray * on each side. Retype it, use one asterisk, or run the text through our markdown to Slack converter before you paste.

There is a space inside the markers. * bold * stays literal. The asterisks must touch the first and last letters.

The markers are in the middle of a word. Typed asterisks inside a word, like un*bold*able, often do not format. Select the part and press Cmd+B instead.

The text is inside code. Slack's developer docs say text in inline code does not use any other formatting, so *bold* wrapped in backticks shows the asterisks.

Format messages with markup is on. In Preferences, Advanced, this setting hides the toolbar and applies formatting only after you send. The message box shows asterisks while you type; the sent message is bold. With two asterisks, the sent message keeps a stray * on each side, so use one. Untick the setting for live formatting.

Other formatting that fails, from headings to pasted ChatGPT text, is covered in Slack markdown not working. To check a message before you post it, paste it into the Markdown to Slack converter, which previews Slack's rules.

How to bold text in Slack on mobile

In the Slack app for iPhone and Android, type one asterisk on each side of the text, the same as on desktop: *bold*, _italic_, ~strike~. The same rules apply, so no spaces inside the markers. We tested double asterisks on desktop only, so one asterisk is the safe choice on a phone. Shortcuts like Cmd+B need a hardware keyboard, such as an iPad with a keyboard attached.

Bold text in Slack bot and API messages

A bot's text and any Block Kit text object of type mrkdwn use Slack's markup: *bold*, _italic_, ~strike~. In our test, **bold** sent through chat.postMessage showed the asterisks, and so did a [text](url) link; mrkdwn links are written <https://slack.green|text>. Slack also has a markdown block ("type": "markdown") that takes standard markdown, so **bold** and ***bold italic*** work there. This chat.postMessage body uses both:

{
  "channel": "C0123456789",
  "text": "Deploy finished",
  "blocks": [
    {"type": "section", "text": {"type": "mrkdwn", "text": "*Deploy finished* in _4 min 12 s_"}},
    {"type": "markdown", "text": "**Next:** check the _error rate_ dashboard"}
  ]
}

To send asterisks without formatting, set "mrkdwn": false on the top-level text, or use a plain_text text object in blocks. Both options are from Slack's developer docs on formatting message text.

See also how to strikethrough in Slack, bullet points and tables. Slack has no spoiler or text color formatting; we tested both in Slack spoiler text and Slack text color.

FAQ

Why does Slack show my asterisks instead of bold?

You pasted the text, left a space inside the asterisks, put them inside code, or a bot sent **bold**. Typed **bold** works in the message box; for pasted text, bots and markup mode, use one asterisk on each side, touching the text.

How do you italicize in Slack?

Press Cmd+I (Ctrl+I), or put underscores around the text: _text_.

Does Slack use markdown for bold?

Partly. In the message box, typed *bold* and **bold** both turn bold. Pasted text, markup mode and bot mrkdwn text need one asterisk. Apps can also send the Block Kit markdown block, which reads **bold**.

Can I make text bigger or change the font in a Slack message?

No. Slack messages have no font size, color or heading options. Each reader sees their own font choice; the options are in what font Slack uses. Bold and a short line of its own are the usual way to make a heading.