Slack Formatting:
How Markdown Works in Slack

Slack formatting cheat sheet

The Slack column is what you type with markup turned on. With the toolbar (the default), select text and click the button or use the keyboard shortcuts instead. You can stack styles on the same text.

Two details catch people. First, Slack has no list markup: in the default toolbar mode you start a bulleted list by typing * and a space, and a numbered list by typing 1. and a space. Slack says list auto-formatting is not applied when markup mode is on. Second, press Shift Enter for a new line. Enter on its own sends the message unless you change your Enter key preference.

What does not work in Slack

• Headings. Slack messages have no heading syntax, so # Title will not become a heading. Use a bold line instead.
• Tables. Pipe tables are not rendered in messages you type. See the tables section below for what does work.
• Images.  is not a Slack format. Upload the image or paste the image URL.
• Markdown double symbols. **bold** and ~~strike~~ are not Slack markup. Slack uses one symbol on each side.
• Formatting inside code. Text inside backticks does not take any other formatting, so *bold* inside `code` stays literal.
• Underline by markup. Underline is on the toolbar, but Slack lists no markup symbol for it.

How to turn on markup (markdown) mode in Slack

If you would rather type symbols than click buttons, switch Slack to markup. On desktop:

1. Click your profile picture in the sidebar.
2. Select Preferences, then Advanced.
3. Under Input Options, check Format messages with markup.

What changes when it is on, according to Slack:

• The formatting toolbar is hidden from the message box.
• Formatting is applied after you send, so you see raw symbols while typing instead of a live preview.
• Automatic formatting for bulleted, numbered and indented lists is not applied.
• Slack notes that “messages that you copy and paste will appear in plain text.”

To go back to the toolbar, uncheck the same box. Slack documents this setting for the desktop app. If you just want to hide or show the toolbar, click the formatting icon in the message field.

Slack formatting keyboard shortcuts

Select the text, then press the keys. The list shortcuts are the same in canvases.

Link tip: if a URL is already on your clipboard, select the words you want to link and paste. Slack turns the selection into a link. Underline is on the toolbar, and Slack lists ⌘ U for it on Mac.

Tables in Slack

Slack messages have no table syntax. A markdown pipe table pasted into the message box arrives as lines of pipes and dashes. You have four real options:

• Canvas. Canvases have a “Create a table” option on their toolbar. Add one to a channel or DM from the plus sign in the conversation header.
• Slack list. Lists can show items in a table layout (rows are items, columns are fields). Lists are available on paid plans.
• Code block. For a quick message, the usual workaround is a plain-text table wrapped in three backticks.
• Apps and bots. Block Kit has a table block (up to 100 rows, 20 cells per row, 10,000 characters), and the markdown block renders pipe tables. Details in the developer section.

How to paste markdown from ChatGPT or Claude into Slack

ChatGPT, Claude and Gemini answer in standard markdown. Slack reads a different syntax, so a pasted answer comes through with double asterisks around every bold phrase, pound signs in front of headings, and bracketed links. Converting it first takes a few seconds:

1. Copy the response from ChatGPT or Claude.
2. Paste it into the Markdown to Slack converter. It turns **bold** into *bold*, ~~strike~~ into ~strike~, and headings into bold lines, and leaves code blocks alone.
3. Copy the result and paste it into Slack.
4. Re-add links with ⌘ Shift U (Ctrl Shift U), or turn on markup mode, which accepts [text](url).

Tables will not survive the trip, since Slack messages cannot show them. Put them in a code block or a canvas. And if the AI text is full of em dashes that give it away, run it through the em dash remover before you post.

Slack markdown for developers: mrkdwn and Block Kit

Messages sent by apps, bots and webhooks use mrkdwn, Slack’s own syntax. It is the default for chat.postMessage text and for text objects with "type": "mrkdwn". Bold, italic, strikethrough, code and quotes follow the cheat sheet above. The differences are links, mentions and escaping.

Links

Bare URLs are linked automatically. For custom link text, use <https://example.com|link text>. Email links work the same way with <mailto:name@example.com|Email me>. The markdown form [text](url) is not mrkdwn.

Mentions

• User: <@U012AB3CD>, shows the display name.
• Channel: <#C123ABC456>, shows the channel name.
• User group: <!subteam^SAZ94GDB8>, notifies every member.
• Special mention: <!here> for active channel members. Use these sparingly.

Slack recommends these ID-based forms over typing names, since names change.

Dates in the reader’s timezone

<!date^timestamp^token_string^optional_link|fallback_text> shows a Unix timestamp in each viewer’s own timezone. Tokens include {date_num}, {date}, {date_short}, {date_long}, {date_pretty}, {time}, {time_secs} and {ago}. The fallback text is required.

<!date^1392734382^{date} at {time}|February 18th, 2014 at 6:39 AM PST>

Escaping and turning formatting off

Only three characters need escaping: & as &, < as < and > as >. To send text with no formatting, use a plain_text text object in blocks, or set "mrkdwn": false for top-level text.

The markdown block: standard markdown for apps

Block Kit now has a markdown block that takes standard markdown and lets Slack translate it. It is built for apps that post LLM output. It supports **bold**, *italic*, ~~strike~~, [text](url) links, # headings (all shown at the same size), ordered, unordered and task lists, code with language highlighting, quotes, --- dividers and pipe tables. Images become plain links using the alt text. All markdown blocks in one payload share a 12,000 character limit, and one block may be split into several after translation.

{
  "blocks": [
    {
      "type": "markdown",
      "text": "## Weekly report\n**Shipped:** 3 features\n\n| Team | Status |\n| --- | --- |\n| Web | Done |"
    }
  ]
}

If you can’t use the markdown block (older integrations, attachments, or mrkdwn text fields), convert the text to mrkdwn first. The Markdown to Slack converter outputs <url|text> links, which is the form the API expects.

Frequently Asked Questions