Introducing Demark: HTML in. MD out. Blink-fast. | Peter Steinberger

I recently found myself needing a component that converts messy, potentially malformed HTML to clean Markdown in Swift. After searching around, I couldn’t find anything that really fit my needs, so I decided to write my own. The result is Demark – my first Swift package that’s now available on the Swift Package Index.

The Problem

HTML to Markdown conversion sounds straightforward, but it’s surprisingly complex when you need to handle:

Malformed or messy HTML
JavaScript-rendered content
Complex nested structures
Various HTML edge cases

I needed something reliable that could handle real-world HTML, not just clean, well-formed markup.

The Solution: Standing on the Shoulders of Giants

Instead of writing a full-blown HTML parser from scratch, I took a different approach. Why reinvent the wheel when there are already excellent JavaScript libraries that solve this problem really well?

Demark leverages two proven JavaScript libraries:

Turndown.js for the most accurate conversions
html-to-md for faster, lightweight processing

The magic happens by running these libraries inside a WKWebView, giving me access to a full browser environment with proper DOM parsing capabilities.

Two Conversion Engines

Demark offers flexibility with two different engines:

Turndown.js (Default) - When you need accuracy:

Full DOM-based parsing
Handles complex HTML and JavaScript-rendered content
Comprehensive configuration options
~100ms for first conversion (then much faster)

html-to-md - When you need speed:

Lightweight JavaScript-based conversion
Much faster performance (~5-10ms per conversion)
Perfect for batch processing simple HTML

Vibe Coding with AI

Here’s the thing – I probably would never have released this without AI assistance. But with AI, the whole process became so much easier. What would have taken me days of tedious work – setting up the package structure, writing documentation, handling edge cases, making it Swift Package Index ready – took me just a few hours.

AI helped me:

Structure the Swift package properly
Write comprehensive documentation
Handle all the WebKit integration details
Create a clean, modern Swift API with async/await
Set up proper error handling

Simple to Use

Despite the complexity under the hood, Demark is dead simple to use. The Swift package that turns down HTML and turns up Markdown – it’s a markup markdown!

import Demark

@MainActor 
func convertHTML() async throws {
    let demark = Demark()
    let html = "<h1>Hello World</h1><p>This is <strong>bold</strong> text.</p>"
    let markdown = try await demark.convertToMarkdown(html)
    print(markdown)
    // Output: # Hello World
    //
    // This is **bold** text.
}

My First Swift Package

Demark works across all Apple platforms: iOS, macOS, watchOS, tvOS, and visionOS.

I’m quite happy about this milestone. After years of iOS development, publishing my first Swift package feels like a natural next step in my open source journey. The fact that it’s now in the Swift Package Index makes it easily discoverable and installable for other developers.

The experience taught me that sometimes the best solution isn’t writing everything from scratch – it’s about cleverly combining existing, battle-tested solutions in a new way.

Try It Out

If you need HTML to Markdown conversion in your Swift projects, give Demark a try. You can add it to your project via Swift Package Manager:

dependencies: [
    .package(url: "https://github.com/steipete/Demark.git", from: "1.0.0")
]

The repository includes an example app with a dual-pane interface where you can test conversions in real-time. Perfect for seeing exactly how your HTML will be transformed.

Here’s to many more Swift packages! 🚀