n8n-nodes-html-to-slack

An n8n community node that converts raw HTML into Slack-compatible mrkdwn formatted text.

Install

In n8n (recommended)

Go to Settings → Community Nodes → Install and enter:

n8n-nodes-html-to-slack

Manual (custom nodes directory)

cd ~/.n8n/custom
pnpm install n8n-nodes-html-to-slack

Usage

Add the HTML to Slack node to your workflow. Connect any node that produces HTML (e.g. an HTTP Request, a webhook body, or a Gmail node) and map its HTML field to the HTML input.

[Webhook] → [HTML to Slack] → [Slack]

The node outputs all original fields plus a new field (default: text) containing the converted mrkdwn string, ready to pass directly to the Slack Send Message node.

Input / Output Example

Input HTML:

<p>Check out <a href="https://slack.com"><strong>Slack</strong></a> and visit https://n8n.io</p>

Output mrkdwn:

Check out <https://slack.com|*Slack*> and visit <https://n8n.io>

Full HTML → mrkdwn Mapping

| HTML | Slack mrkdwn | |-----------------------------------|-------------------------------------------| | <b>, <strong> | *text* | | <i>, <em> | _text_ | | <s>, <del>, <strike> | ~text~ | | <code> (inline) | `code` | | <pre> | ```\ncode\n``` | | <a href="U">T</a> | <U\|T> (named link) | | <a href="U">U</a> | <U> (text equals href) | | <a href="mailto:x">T</a> | <mailto:x\|T> | | Bare URL in text | <URL> (post-processed) | | <blockquote> | > prefix on each line | | <ul><li> | • item | | <ol><li> | 1. item, 2. item … | | <h1>–<h6> | See headingStyle option | | <table> | See tableHandling option | | <img> | See imageHandling option | | <br> | \n | | <p> | content + \n\n | | <hr> | ─────────────── | | <div>, <span>, <section> … | Tags stripped, inner text preserved | | HTML entities (&, < …) | Decoded before conversion |

Slack mrkdwn Limitations

Slack's mrkdwn format is a subset of Markdown — several HTML features have no equivalent:

• No headings — <h1>–<h6> are approximated as bold text
• No tables — flattened to tab-separated plain text or stripped
• No inline images — replaced with alt text, a link, or stripped
• No underline — <u> content is preserved as plain text
• No text colours — style attributes are ignored
• All URLs must use angle-bracket syntax — bare URLs are not reliably auto-linked when posted via the API; this node wraps them automatically

Options Reference

| Option | Values | Default | Description | |-------------------|-------------------------------------------------|---------------|--------------------------------------------------------------| | headingStyle | bold | boldWithSeparator | strip | bold | bold → *text*; boldWithSeparator adds a ─── divider; strip removes headings entirely | | tableHandling | plainText | strip | plainText | plainText flattens cells tab-separated; strip removes the whole table | | imageHandling | altText | asLink | strip | altText | altText uses the alt attribute; asLink wraps src as <url>; strip removes the image | | trimWhitespace | true | false | true | Collapses 3+ consecutive newlines to a single blank line and trims the result |

Development

# Clone and install
git clone https://github.com/<you>/n8n-nodes-html-to-slack.git
cd n8n-nodes-html-to-slack
pnpm install

# Unit tests (vitest, no n8n required)
pnpm test

# Hot-reload dev server (starts local n8n with this node loaded)
pnpm dev

# Type-check + build
pnpm run build

# Lint
pnpm run lint

File structure

nodes/HtmlToSlack/
├── HtmlToSlack.node.ts   — n8n integration layer
├── HtmlToSlack.node.json — codex / search metadata
├── htmlToMrkdwn.ts       — pure conversion logic (zero n8n deps)
├── htmlToMrkdwn.test.ts  — vitest unit tests
└── htmlToSlack.svg       — node icon

htmlToMrkdwn.ts has no n8n imports and can be used as a standalone library outside of n8n.

License

MIT