Markdown to HTML Conversion

Expert skill for converting Markdown documents to HTML using the marked.js library, or writing data conversion scripts; in this case scripts similar to markedJS/marked repository. For custom scripts knowledge is not confined to marked.js, but data conversion methods are utilized from tools like pandoc and gomarkdown/markdown for data conversion; jekyll/jekyll and gohugoio/hugo for templating systems.

The conversion script or tool should handle single files, batch conversions, and advanced configurations.

When to Use This Skill

• User asks to "convert markdown to html" or "transform md files"
• User wants to "render markdown" as HTML output
• User needs to generate HTML documentation from .md files
• User is building static sites from Markdown content
• User is building template system that converts markdown to html
• User is working on a tool, widget, or custom template for an existing templating system
• User wants to preview Markdown as rendered HTML

Converting Markdown to HTML

Essential Basic Conversions

For more see basic-markdown-to-html.md

    ```markdown
    # Level 1
    ## Level 2

    One sentence with a [link](https://example.com), and a HTML snippet like `<p>paragraph tag</p>`.

    - `ul` list item 1
    - `ul` list item 2

    1. `ol` list item 1
    2. `ol` list item 1

    | Table Item | Description |
    | One | One is the spelling of the number `1`. |
    | Two | Two is the spelling of the number `2`. |

    ```js
    var one = 1;
    var two = 2;

    function simpleMath(x, y) {
     return x + y;
    }
    console.log(simpleMath(one, two));
    ```
    ```

    ```html
    <h1>Level 1</h1>
    <h2>Level 2</h2>

    <p>One sentence with a <a href="https://example.com">link</a>, and a HTML snippet like <code>&lt;p&gt;paragraph tag&lt;/p&gt;</code>.</p>

    <ul>
     <li>`ul` list item 1</li>
     <li>`ul` list item 2</li>
    </ul>

    <ol>
     <li>`ol` list item 1</li>
     <li>`ol` list item 2</li>
    </ol>

    <table>
     <thead>
      <tr>
       <th>Table Item</th>
       <th>Description</th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td>One</td>
       <td>One is the spelling of the number `1`.</td>
      </tr>
      <tr>
       <td>Two</td>
       <td>Two is the spelling of the number `2`.</td>
      </tr>
     </tbody>
    </table>

    <pre>
     <code>var one = 1;
     var two = 2;

     function simpleMath(x, y) {
      return x + y;
     }
     console.log(simpleMath(one, two));</code>
    </pre>
    ```

Code Block Conversions

For more see code-blocks-to-html.md

    ```markdown
    your code here
    ```

    ```html
    <pre><code class="language-md">
    your code here
    </code></pre>
    ```

    ```js
    console.log("Hello world");
    ```

    ```html
    <pre><code class="language-js">
    console.log("Hello world");
    </code></pre>
    ```

    ```markdown
      ```

      ```
      visible backticks
      ```

      ```
    ```

    ```html
      <pre><code>
      ```

      visible backticks

      ```
      </code></pre>
    ```

Collapsed Section Conversions

For more see collapsed-sections-to-html.md

    ```markdown
    <details>
    <summary>More info</summary>

    ### Header inside

    - Lists
    - **Formatting**
    - Code blocks

        ```js
        console.log("Hello");
        ```

    </details>
    ```

    ```html
    <details>
    <summary>More info</summary>

    <h3>Header inside</h3>

    <ul>
     <li>Lists</li>
     <li><strong>Formatting</strong></li>
     <li>Code blocks</li>
    </ul>

    <pre>
     <code class="language-js">console.log("Hello");</code>
    </pre>

    </details>
    ```

Mathematical Expression Conversions

For more see writing-mathematical-expressions-to-html.md

    ```markdown
    This sentence uses `$` delimiters to show math inline: $\sqrt{3x-1}+(1+x)^2$
    ```

    ```html
    <p>This sentence uses <code>$</code> delimiters to show math inline:
     <math-renderer><math xmlns="http://www.w3.org/1998/Math/MathML">
      <msqrt><mn>3</mn><mi>x</mi><mo>−</mo><mn>1</mn></msqrt>
      <mo>+</mo><mo>(</mo><mn>1</mn><mo>+</mo><mi>x</mi>
      <msup><mo>)</mo><mn>2</mn></msup>
     </math>
    </math-renderer>
    </p>
    ```

    ```markdown
    **The Cauchy-Schwarz Inequality**\
    $$\left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)$$
    ```

    ```html
    <p><strong>The Cauchy-Schwarz Inequality</strong><br>
     <math-renderer>
      <math xmlns="http://www.w3.org/1998/Math/MathML">
       <msup>
        <mrow><mo>(</mo>
         <munderover><mo data-mjx-texclass="OP">∑</mo>
          <mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow><mi>n</mi>
         </munderover>
         <msub><mi>a</mi><mi>k</mi></msub>
         <msub><mi>b</mi><mi>k</mi></msub>
         <mo>)</mo>
        </mrow>
        <mn>2</mn>
       </msup>
       <mo>≤</mo>
       <mrow><mo>(</mo>
        <munderover><mo>∑</mo>
         <mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow>
         <mi>n</mi>
        </munderover>
        <msubsup><mi>a</mi><mi>k</mi><mn>2</mn></msubsup>
        <mo>)</mo>
       </mrow>
       <mrow><mo>(</mo>
         <munderover><mo>∑</mo>
          <mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow>
          <mi>n</mi>
         </munderover>
         <msubsup><mi>b</mi><mi>k</mi><mn>2</mn></msubsup>
         <mo>)</mo>
       </mrow>
      </math>
     </math-renderer></p>
    ```

Table Conversions

For more see tables-to-html.md

    ```markdown
    | First Header  | Second Header |
    | ------------- | ------------- |
    | Content Cell  | Content Cell  |
    | Content Cell  | Content Cell  |
    ```

    ```html
    <table>
     <thead><tr><th>First Header</th><th>Second Header</th></tr></thead>
     <tbody>
      <tr><td>Content Cell</td><td>Content Cell</td></tr>
      <tr><td>Content Cell</td><td>Content Cell</td></tr>
     </tbody>
    </table>
    ```

    ```markdown
    | Left-aligned | Center-aligned | Right-aligned |
    | :---         |     :---:      |          ---: |
    | git status   | git status     | git status    |
    | git diff     | git diff       | git diff      |
    ```

    ```html
    <table>
      <thead>
       <tr>
        <th align="left">Left-aligned</th>
        <th align="center">Center-aligned</th>
        <th align="right">Right-aligned</th>
       </tr>
      </thead>
      <tbody>
       <tr>
        <td align="left">git status</td>
        <td align="center">git status</td>
        <td align="right">git status</td>
       </tr>
       <tr>
        <td align="left">git diff</td>
        <td align="center">git diff</td>
        <td align="right">git diff</td>
       </tr>
      </tbody>
    </table>
    ```

Working with markedJS/marked

Prerequisites

• Node.js installed (for CLI or programmatic usage)
• Install marked globally for CLI: npm install -g marked
• Or install locally: npm install marked

Quick Conversion Methods

See marked.md Quick Conversion Methods

Step-by-Step Workflows

See marked.md Step-by-Step Workflows

CLI Configuration

Using Config Files

Create ~/.marked.json for persistent options:

{
  "gfm": true,
  "breaks": true
}

Or use a custom config:

marked -i input.md -o output.html -c config.json

CLI Options Reference

Security Warning

⚠️ Marked does NOT sanitize output HTML. For untrusted input, use a sanitizer:

import { marked } from 'marked';
import DOMPurify from 'dompurify';

const unsafeHtml = marked.parse(untrustedMarkdown);
const safeHtml = DOMPurify.sanitize(unsafeHtml);

Recommended sanitizers:

• DOMPurify (recommended)
• sanitize-html
• js-xss

Supported Markdown Flavors

Troubleshooting

Working with pandoc

Prerequisites

• Pandoc installed (download from https://pandoc.org/installing.html)
• For PDF output: LaTeX installation (MacTeX on macOS, MiKTeX on Windows, texlive on Linux)
• Terminal/command prompt access

Quick Conversion Methods

Method 1: CLI Basic Conversion

# Convert markdown to HTML
pandoc input.md -o output.html

# Convert with standalone document (includes header/footer)
pandoc input.md -s -o output.html

# Explicit format specification
pandoc input.md -f markdown -t html -s -o output.html

Method 2: Filter Mode (Interactive)

# Start pandoc as a filter
pandoc

# Type markdown, then Ctrl-D (Linux/macOS) or Ctrl-Z+Enter (Windows)
Hello *pandoc*!
# Output: <p>Hello <em>pandoc</em>!</p>

Method 3: Format Conversion

# HTML to Markdown
pandoc -f html -t markdown input.html -o output.md

# Markdown to LaTeX
pandoc input.md -s -o output.tex

# Markdown to PDF (requires LaTeX)
pandoc input.md -s -o output.pdf

# Markdown to Word
pandoc input.md -s -o output.docx

CLI Configuration

Security Warning

⚠️ Pandoc processes input faithfully. When converting untrusted markdown:

• Use --sandbox mode to disable external file access
• Validate input before processing
• Sanitize HTML output if displayed in browsers

# Run in sandbox mode for untrusted input
pandoc --sandbox input.md -o output.html

Supported Markdown Flavors

Troubleshooting

Working with gomarkdown/markdown

Prerequisites

• Go 1.18 or higher installed
• Install the library: go get github.com/gomarkdown/markdown
• For CLI tool: go install github.com/gomarkdown/mdtohtml@latest

Quick Conversion Methods

Method 1: Simple Conversion (Go)

package main

import (
    "fmt"
    "github.com/gomarkdown/markdown"
)

func main() {
    md := []byte("# Hello World\n\nThis is **bold** text.")
    html := markdown.ToHTML(md, nil, nil)
    fmt.Println(string(html))
}

Method 2: CLI Tool

# Install mdtohtml
go install github.com/gomarkdown/mdtohtml@latest

# Convert file
mdtohtml input.md output.html

# Convert file (output to stdout)
mdtohtml input.md

Method 3: Custom Parser and Renderer

package main

import (
    "github.com/gomarkdown/markdown"
    "github.com/gomarkdown/markdown/html"
    "github.com/gomarkdown/markdown/parser"
)

func mdToHTML(md []byte) []byte {
    // Create parser with extensions
    extensions := parser.CommonExtensions | parser.AutoHeadingIDs | parser.NoEmptyLineBeforeBlock
    p := parser.NewWithExtensions(extensions)
    doc := p.Parse(md)

    // Create HTML renderer with extensions
    htmlFlags := html.CommonFlags | html.HrefTargetBlank
    opts := html.RendererOptions{Flags: htmlFlags}
    renderer := html.NewRenderer(opts)

    return markdown.Render(doc, renderer)
}

CLI Configuration

The mdtohtml CLI tool has minimal options:

mdtohtml input-file [output-file]

For advanced configuration, use the Go library programmatically with parser and renderer options:

Security Warning

⚠️ gomarkdown does NOT sanitize output HTML. For untrusted input, use Bluemonday:

import (
    "github.com/microcosm-cc/bluemonday"
    "github.com/gomarkdown/markdown"
)

maybeUnsafeHTML := markdown.ToHTML(md, nil, nil)
html := bluemonday.UGCPolicy().SanitizeBytes(maybeUnsafeHTML)

Recommended sanitizer: Bluemonday

Supported Markdown Flavors

Troubleshooting

Working with jekyll

Prerequisites

• Ruby version 2.7.0 or higher
• RubyGems
• GCC and Make (for native extensions)
• Install Jekyll and Bundler: gem install jekyll bundler

Quick Conversion Methods

Method 1: Create New Site

# Create a new Jekyll site
jekyll new myblog

# Change to site directory
cd myblog

# Build and serve locally
bundle exec jekyll serve

# Access at http://localhost:4000

Method 2: Build Static Site

# Build site to _site directory
bundle exec jekyll build

# Build with production environment
JEKYLL_ENV=production bundle exec jekyll build

Method 3: Live Reload Development

# Serve with live reload
bundle exec jekyll serve --livereload

# Serve with drafts
bundle exec jekyll serve --drafts

CLI Configuration

Security Warning

⚠️ Jekyll security considerations:

• Avoid using safe: false in production
• Use exclude in _config.yml to prevent sensitive files from being published
• Sanitize user-generated content if accepting external input
• Keep Jekyll and plugins updated

# _config.yml security settings
exclude:
  - Gemfile
  - Gemfile.lock
  - node_modules
  - vendor

Supported Markdown Flavors

Configure markdown processor in _config.yml:

markdown: kramdown
kramdown:
  input: GFM
  syntax_highlighter: rouge

Troubleshooting

Working with hugo

Prerequisites

• Hugo installed (download from https://gohugo.io/installation/)
• Git (recommended for themes and modules)
• Go (optional, for Hugo Modules)

Quick Conversion Methods

Method 1: Create New Site

# Create a new Hugo site
hugo new site mysite

# Change to site directory
cd mysite

# Add a theme
git init
git submodule add https://github.com/theNewDynamic/gohugo-theme-ananke themes/ananke
echo "theme = 'ananke'" >> hugo.toml

# Create content
hugo new content posts/my-first-post.md

# Start development server
hugo server -D

Method 2: Build Static Site

# Build site to public directory
hugo

# Build with minification
hugo --minify

# Build for specific environment
hugo --environment production

Method 3: Development Server

# Start server with drafts
hugo server -D

# Start with live reload and bind to all interfaces
hugo server --bind 0.0.0.0 --baseURL http://localhost:1313/

# Start with specific port
hugo server --port 8080

CLI Configuration

Security Warning

⚠️ Hugo security considerations:

• Configure security policy in hugo.toml for external commands
• Use --enableGitInfo carefully with public repositories
• Validate shortcode parameters for user-generated content

# hugo.toml security settings
[security]
  enableInlineShortcodes = false
  [security.exec]
    allow = ['^go$', '^npx$', '^postcss$']
  [security.funcs]
    getenv = ['^HUGO_', '^CI$']
  [security.http]
    methods = ['(?i)GET|POST']
    urls = ['.*']

Supported Markdown Flavors

Configure markdown in hugo.toml:

[markup]
  [markup.goldmark]
    [markup.goldmark.extensions]
      definitionList = true
      footnote = true
      linkify = true
      strikethrough = true
      table = true
      taskList = true
    [markup.goldmark.renderer]
      unsafe = false  # Set true to allow raw HTML

Troubleshooting

References

Writing and Styling Markdown

• basic-markdown.md
• code-blocks.md
• collapsed-sections.md
• tables.md
• writing-mathematical-expressions.md
• Markdown Guide: https://www.markdownguide.org/basic-syntax/
• Styling Markdown: https://github.com/sindresorhus/github-markdown-css

markedJS/marked

• Official documentation: https://marked.js.org/
• Advanced options: https://marked.js.org/using_advanced
• Extensibility: https://marked.js.org/using_pro
• GitHub repository: https://github.com/markedjs/marked

pandoc

• Getting started: https://pandoc.org/getting-started.html
• Official documentation: https://pandoc.org/MANUAL.html
• Extensibility: https://pandoc.org/extras.html
• GitHub repository: https://github.com/jgm/pandoc

gomarkdown/markdown

• Official documentation: https://pkg.go.dev/github.com/gomarkdown/markdown
• Advanced configuration: https://pkg.go.dev/github.com/gomarkdown/markdown@v0.0.0-20250810172220-2e2c11897d1a/html
• Markdown processing: https://blog.kowalczyk.info/article/cxn3/advanced-markdown-processing-in-go.html
• GitHub repository: https://github.com/gomarkdown/markdown

jekyll

• Official documentation: https://jekyllrb.com/docs/
• Configuration options: https://jekyllrb.com/docs/configuration/options/
• Plugins: https://jekyllrb.com/docs/plugins/
  • Installation
  • Generators
  • Converters
  • Commands
  • Tags
  • Filters
  • Hooks
• GitHub repository: https://github.com/jekyll/jekyll

hugo

• Official documentation: https://gohugo.io/documentation/
• All Settings: https://gohugo.io/configuration/all/
• Editor Plugins: https://gohugo.io/tools/editors/
• GitHub repository: https://github.com/gohugoio/hugo