majiayu000 Slack Message Formatter
Format messages for Slack with pixel-perfect accuracy. Converts Markdown to Slack-compatible output with two delivery paths:
- Copy-paste — Rich HTML that preserves formatting when pasted into Slack's compose box
- API/Webhook — Slack mrkdwn syntax for bots, automation, and CI/CD
When to Use This Skill
- User asks to write a Slack message, announcement, or notification
- User asks to format something "for Slack"
- User wants to preview how a message will look in Slack
- User wants to send a message via Slack webhook
- User has Markdown content they want to share in Slack
What This Skill Does
- Generates content in Markdown — Claude writes the message in standard Markdown, its native format
- Converts to Rich HTML — Transforms Markdown into rich HTML that preserves formatting when pasted into Slack's compose box
- Converts to Slack mrkdwn — Transforms Markdown into Slack's proprietary mrkdwn syntax for API/webhook delivery
- Generates a Slack-themed preview — Creates an HTML preview page styled like the Slack UI and opens it in the browser
- Copies to clipboard — Automatically copies the rich HTML to the system clipboard for one-step paste into Slack
How to Use
Basic Usage
Write a Slack message announcing our Q2 product launch
Format this for Slack: We shipped 3 new features this week...
Create a Slack announcement for the engineering team about the new CI pipeline
Webhook/API Delivery
Send a deploy notification to Slack via webhook
Formatting Features
The converter handles all Markdown features and translates them correctly for Slack:
- Bold, italic, strikethrough, inline code
- Links and headings (converted to bold in Slack)
- Tables (rich HTML tables for paste, code blocks for API)
- Task lists with emoji checkboxes
- Nested lists and blockquotes
- Code blocks with syntax highlighting
- Slack mentions (
<@U012AB3CD>,<!here>,<!channel>) - 150+ emoji shortcodes converted to Unicode
Example
User: "Write a Slack message announcing our new feature"
Output (opened as a Slack-themed preview in the browser + copied to clipboard):
The preview shows a pixel-perfect Slack UI rendering. The user pastes directly into Slack with Cmd+V / Ctrl+V and the formatting is preserved.
User: "Send a deploy notification to our #deploys channel via webhook"
Output (sent via mrkdwn to the configured webhook):
*:rocket: Deploy Successful*
*Service:* payment-api
*Version:* v2.5.1
*Environment:* production
*Duration:* 47s
:white_check_mark: All health checks passing
Configuration
| Env Variable | Default | Description |
|---|---|---|
SLACK_FORMATTER_CLIPBOARD |
true |
Set to false to disable auto-clipboard copy |
SLACK_FORMATTER_PREVIEW_DIR |
/tmp/slack-formatter |
Directory for preview HTML files |
CCH_SLA_WEBHOOK |
(none) | Slack webhook URL for sending messages |
Tips
- Always let the converter handle the Markdown-to-Slack translation; never write mrkdwn or HTML by hand
- Slack mentions (
<@U...>,<#C...>,<!here>) can be included directly in the Markdown - Tables work beautifully via the copy-paste path; for API delivery they become code blocks (Slack has no table syntax)
- Preview files are timestamped so you can revisit them from conversation history