mrkdwnify

A Python library for converting standard Markdown into Slack's mrkdwn format — the exact syntax Slack uses to render bold, italic, links, code blocks, lists, and more.

Built specifically for AI bots and Slack integrations where LLM output (always in Markdown) needs to render correctly in Slack without manual post-processing.

Installation

pip install mrkdwnify

Quick Start

from mrkdwnify import mrkdwnify

text = mrkdwnify("""
# Deploy Complete

**my-service** v1.2 is live in production.

Changes in this release:
- Fixed *authentication* bug
- Improved ~~old caching~~ new caching layer
- Added `health-check` endpoint

> Review the [full changelog](https://example.com/changelog)
""")

print(text)

Output (renders correctly in Slack):

*Deploy Complete*

*my-service* v1.2 is live in production.

Changes in this release:
•   Fixed _authentication_ bug
•   Improved ~old caching~ new caching layer
•   Added `health-check` endpoint

> Review the <https://example.com/changelog|full changelog>

Conversion Reference

Markdown	Slack mrkdwn
# Heading	*Heading*
**Bold**	*Bold*
*Italic*	_Italic_
~~Strike~~	~Strike~
`code`	`code`
``` block ```	``` block ```
[Link](https://example.com)	<https://example.com|Link>
	<https://example.com/img.png|img>
> blockquote	> blockquote
- item	• item
1. item	1. item
<@U12345>	<@U12345> (preserved)
<#C12345|general>	<#C12345|general> (preserved)

Features

• Converts all standard Markdown to valid Slack mrkdwn
• Preserves Slack-native mentions (<@user>, <#channel>, <!here>, <!channel>)
• Handles GFM strikethrough (~~text~~ → ~text~)
• Strips heading hierarchy (all headings become bold — Slack has no heading levels)
• Suppresses redundant bold markers inside headings to avoid double **
• Correctly escapes &, <, > as HTML entities where required by Slack
• Strips unsupported syntax cleanly (no broken output)
• Handles reference-style links and images
• Tested across Python 3.9–3.13

Usage with AI Bots

LLMs output Markdown. Slack expects mrkdwn. mrkdwnify is the bridge:

from mrkdwnify import mrkdwnify
import anthropic

client = anthropic.Anthropic()

message = client.messages.create(
    model="claude-opus-4-6",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Summarize today's deployments"}],
)

# Convert AI response (Markdown) to Slack-ready mrkdwn
slack_text = mrkdwnify(message.content[0].text)

# Post to Slack
slack_client.chat_postMessage(channel="#deployments", text=slack_text)

Contributing

Contributions are welcome! Please open an issue first to discuss what you'd like to change.

1. Fork the repository
2. Create a feature branch (git checkout -b feature/my-feature)
3. Commit your changes (git commit -m 'Add my feature')
4. Push to the branch (git push origin feature/my-feature)
5. Open a Pull Request

License

MIT License — see LICENSE for details.