Slack Markdown Not Working? Why and How to Fix It

Slack markdown usually "stops working" because Slack messages never used standard markdown. Slack has its own markup: one asterisk on each side for bold (*bold*), underscores for italics (_italic_), one tilde for strikethrough (~strike~), backticks for code, and > for a quote. Standard markdown such as **bold**, # Heading, ~~strike~~ and pipe tables shows up as the characters you typed. If your syntax is right and it still does not format, the cause is a setting or the way you pasted: press Cmd+Shift+F (Ctrl+Shift+F on Windows) after pasting to apply formatting, and check Format messages with markup in Preferences > Advanced.

The syntax and the setting are 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.

While you fix formatting, keep in mind that Slack sets you to away after about 10 minutes without input in the Slack window. Slack Green keeps your status green from a server during the hours you set.

Slack formatting not working: symptom, cause and fix

Does Slack support markdown?

Partly. Slack's markup borrows some markdown characters and changes others. What works in a message you type:

• • Bold *text*, italic _text_, strikethrough ~text~
• • Inline code with one backtick on each side, and code blocks with three
• • A quote with > at the start of a line
• • A bulleted list with * and a space, a numbered list with 1. and a space
• • A link as [text](url), which Slack's help lists for markup mode

What does not work: **bold**, __bold__, ~~strike~~, headings, tables, images and horizontal rules. Each style has its own guide: bold and italics, bullet points, quotes and tables.

Fix pasted markdown that does not format

When you paste text, Slack keeps markup characters as plain text. Slack's shortcut list has an action for this: Apply markdown formatting, Cmd+Shift+F on a Mac and Ctrl+Shift+F on Windows and Linux. Paste, press the shortcut, and Slack formats the pasted markup. If it goes wrong, Undo formatting is Cmd+Z (Ctrl+Z).

Text from ChatGPT, Claude, Notion or a GitHub README is written in standard markdown, with double asterisks and # headings, which Slack's markup does not read. Convert it first: paste it into our markdown to Slack converter, press Copy for Slack, and paste the result. Headings become bold lines and tables become aligned code blocks. The ChatGPT case, with a prompt that makes it write in Slack format, is in how to paste ChatGPT into Slack.

The Format messages with markup setting

Slack has two ways to format. By default, the formatting toolbar is on and typed markers turn into formatting as you type. With Format messages with markup on, Slack's help says three things change:

To change it: click your profile picture, choose Preferences, select Advanced, and under Input Options tick or untick Format messages with markup.

How to turn off Slack formatting

To send the characters themselves, not the formatting:

Slack markdown not rendering in bot or API messages

Slack's developer docs list three switches that decide whether a bot's text is formatted:

Slack also treats &, < and > as control characters. Escape them in text you pass through, or a stray < can swallow part of the message:

def slack_escape(text: str) -> str:
    """Escape the three characters Slack treats as control characters."""
    return text.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;")


payload = {
    "channel": "C0123456789",
    "text": "*Build failed* for " + slack_escape("feature/a<b & c>"),
}
print(payload["text"])

Before a bot sends a message, paste its text into the Slack message formatter to preview how Slack renders it.

FAQ

Why is my Slack markdown not working?

Slack uses its own markup, not standard markdown. Bold is *one asterisk*, and headings and tables do not exist in messages.

How do I apply formatting to pasted text in Slack?

Paste, then press Cmd+Shift+F on a Mac or Ctrl+Shift+F on Windows and Linux (Apply markdown formatting).

How do I turn off markdown in Slack?

Press Cmd+Z right after Slack formats your text, wrap the text in backticks, or turn on Format messages with markup in Preferences, Advanced.

Does Slack support markdown headings?

Not in messages. Use a short bold line. Canvases and the Block Kit markdown block do support headings.

Why does my Slack bot show asterisks?

The text is plain_text or the message has "mrkdwn": false. Use a mrkdwn text object, or send standard markdown in a markdown block.