Docsloth is a Swift wrapper for markdown-it and Asciidoctor.js, which convert Markdown and AsciiDoc into HTML and support a wide range of features and plugins.

In additions, Docsloth's UI module provides a convenient way to display rendered HTML content, which is a WKWebView wrapper and fully supports text selection and copy & paste. Plus, you can easily customize the appearance using CSS.

Docsloth is slow because it's a Swift wrapper around JavaScript libraries. It is much slower than native Swift libraries such as Ink or swift-markdown. It also consumes more memory. You can find the benchmark results here.

The main advantage of Docsloth is that it is powered by well-maintained JavaScript libraries, which offer a rich set of features and are supported by large communities. We also provide a way to configure these libraries and their plugins directly through Swift.

Therefore, Docsloth is suitable for apps that require advanced rendering features but are not very sensitive to performance.

This is how to convert Markdown to HTML:

import DocslothMarkdownItGFMCJKFriendly

let markdownIt = MarkdownIt()
try await markdownIt.setup()
let html = markdownIt.convertToHTML("# Hello, Docsloth!")
print(html) // <h1>Hello, Docsloth!</h1>

You can also customize options and plugins:

import DocslothMarkdownItGFMCJKFriendly

let markdownIt = MarkdownIt(options: MarkdownItOptions(
    base: [
        "linkify": false,
        "breaks": true,
    ],
    plugins: [
        // Options for `markdown-it-task-checkbox`
        .githubAlerts: [
            "matchCaseSensitive": true
        ]
    ],
    // This disables the emoji plugin
    disablePlugins: [.emoji]
))

This is how you can convert AsciiDoc to HTML:

import DocslothAsciidoctor

let asciidoctor = DocslothAsciidoctor()
try await asciidoctor.setup()
let html = asciidoctor.convertToHTML("= Hello, Docsloth!")

print(html) // <h1>Hello, Docsloth!</h1>

You can display the rendered HTML content in SwiftUI using DocslothView:

import SwiftUI
import DocslothUI
import DocslothMarkdownItGFMCJKFriendly

struct ContentView: View {
    @State private var markdownIt = MarkdownIt()

    var body: some View {
        DocslothView(
            source: "# Hello, Docsloth!",
            converter: markdownIt
        )
        .docslothStyle(DocslothGitHubStyle())
        .task {
            try? await markdownIt.setup()
        }
    }
}

You can also find working examples in Examples.

Docsloth consists of many modules so you don't need to import unnecessary ones. These are base modules:

• DocslothUI: Provides the DocslothView for SwiftUI integration. This doesn't include any styles by default, so you can customize the appearance using CSS. If you want a pre-defined style, you can import DocslothGitHubStyle to use.
• DocslothGitHubStyle: A pre-defined style for the DocslothView that is similar to GitHub's style.

Also, there are several converter modules:

• markdown-it
  • DocslothMarkdownIt: A module for rendering Markdown without any additional plugins.
  • DocslothMarkdownItGFM: A module for rendering GitHub's GFM with these plugins:
    • markdown-it-emoji
    • markdown-it-footnote
    • markdown-it-github-alerts
    • markdown-it-task-checkbox
    • @mshibanami-org/markdown-it-sanitize-html
  • DocslothMarkdownItGFMCJKFriendly: A module for rendering GFM with improved support for CJK characters. This uses the same plugins as DocslothMarkdownItGFM plus:
    • markdown-it-cjk-friendly
• Asciidoctor.js
  • DocslothAsciidoctor: A module for rendering AsciiDoc content without any additional plugins.

Both MarkdownIt and Asciidoctor keeps JavaScriptCore's JSContext in memory, and once you call setup(), you can use it everywhere in your app. So, you should create a single instance and reuse it.

In Docsloth, "GFM" refers to GitHub's GitHub Flavored Markdown, not cmark-gfm. As of 2025, cmark-gfm hasn't been updated since 2023 and it doesn't support some features GitHub has, such as Alerts. Docsloth rather tries to follow what GitHub actually supports.

Also, we focus on GFM which is applied to rendering Markdown files such as README.md on github.com. So, some features may not be available in Docsloth, such as mention.

It means that the converter uses a plugin to handle CJK (Chinese, Japanese, Korean) languages more effectively. This is especially useful for texts generated by LLMs, which often lack spaces between words in CJK languages.

You can simply copy & paste our GitHub style to your project and modify it as you like. Then, load your style to DocslothView:

DocslothView(...)
    .docslothStyle(yourCustomTheme)

Docsloth's own code is licensed under the MIT License. See LICENSE.txt for details.

The licenses of each port's dependencies are provided in JSON format in js/dist.

We only use dependencies with permissive licenses, such as MIT, Apache License 2.0, BSD, and ISC.