html_to_markdown_ffi 1.1.0

A high-performance HTML to Markdown converter for Dart and Flutter, powered by Rust FFI.

html_to_markdown

High-performance HTML to Markdown converter for Dart and Flutter, powered by the Rust html-to-markdown engine via FFI bindings. 150-280 MB/s throughput — 10-80x faster than pure Dart alternatives.

Features

• Blazing fast: Rust-powered conversion engine via FFI
• Byte-identical output: Matches the Rust core exactly for all input
• Full metadata extraction: Title, description, author, keywords, OpenGraph, JSON-LD
• Comprehensive options: 40+ conversion settings (heading style, code blocks, links, whitespace, etc.)
• Visitor pattern: Customize element-level conversion behavior
• Cross-platform: Android, iOS, macOS, Linux, Windows

Installation

dart pub add html_to_markdown

Quick Start

import 'package:html_to_markdown/html_to_markdown.dart';

void main() {
  final html = '<h1>Hello World</h1><p>This is a <strong>test</strong>.</p>';

  // Basic conversion
  final result = convert(html);
  print(result.content);
  // # Hello World
  //
  // This is a **test**.
}

Configuration

final options = ConversionOptions()
  ..headingStyle = HeadingStyle.setext
  ..linkStyle = LinkStyle.referenced
  ..extractMetadata = true
  ..wrap = true
  ..wrapWidth = 80;

final result = convert(html, options: options);

Metadata Extraction

final options = ConversionOptions()..extractMetadata = true;
final result = convert(htmlWithMeta, options: options);

print(result.metadata?.title);       // Page title
print(result.metadata?.description); // Meta description
print(result.metadata?.author);      // Author
print(result.metadata?.keywords);    // Keywords list

Custom Visitor

class ScriptStripper extends Visitor {
  @override
  VisitResult visitElementStart(NodeContext ctx) {
    if (ctx.tagName == 'script' || ctx.tagName == 'style') {
      return VisitResult.skip;
    }
    return VisitResult.continue_;
  }
}

final result = convert(html, visitor: ScriptStripper());

Platform Support

Platform	Arch	Status
macOS	arm64, x64	✓ (binary bundled)
iOS (device)	arm64	✓ (static lib bundled)
iOS Simulator	arm64, x64	✓ (static lib bundled)
Android	arm64-v8a, armeabi-v7a, x86_64	✓ (.so bundled)
Linux	arm64, x64	✓ (build from source)
Windows	x64	✓ (build from source)
Web	—	Not supported (use WASM binding)

Native libraries

Prebuilt native binaries are shipped inside the package under native/, so the library is already there when the package is installed — no download step or manual toolchain setup is needed on the supported platforms:

native/
├── include/html_to_markdown.h          # C header (for custom integration)
├── macos-x64/libhtml_to_markdown_ffi.dylib
├── macos-arm64/libhtml_to_markdown_ffi.dylib
├── ios/
│   ├── ios-arm64.a                     # device
│   ├── ios-sim-arm64.a                 # Apple Silicon simulator
│   └── ios-sim-x64.a                   # Intel simulator
└── android/
    ├── arm64-v8a/libhtml_to_markdown_ffi.so
    ├── armeabi-v7a/libhtml_to_markdown_ffi.so
    └── x86_64/libhtml_to_markdown_ffi.so

• macOS — the correct dylib for the host architecture is loaded automatically from the package directory. Nothing to do.

• Android — copy the .so file(s) you need into your app's jniLibs; the loader resolves libhtml_to_markdown_ffi.so from the Android loader path:

  cp native/android/arm64-v8a/libhtml_to_markdown_ffi.so \
     <your-app>/android/app/src/main/jniLibs/arm64-v8a/
  cp native/android/armeabi-v7a/libhtml_to_markdown_ffi.so \
     <your-app>/android/app/src/main/jniLibs/armeabi-v7a/
  cp native/android/x86_64/libhtml_to_markdown_ffi.so \
     <your-app>/android/app/src/main/jniLibs/x86_64/
  

• iOS — iOS uses a static library linked into the app at build time (not dlopen'd). Add the .a for your target to the Runner (e.g. ios/Runner/ Frameworks + the Xcode "Link Binary With Libraries" build phase); the loader then finds the symbols via DynamicLibrary.process():

  • device: native/ios/ios-arm64.a
  • Apple Silicon simulator: native/ios/ios-sim-arm64.a
  • Intel simulator: native/ios/ios-sim-x64.a

Native library resolution order

NativeLibrary tries, in order:

1. HTML_TO_MARKDOWN_FFI_LIB_PATH env var (testing / custom paths)
2. Bundled binary — native/<rid>/libhtml_to_markdown_ffi.* shipped inside the package (macOS arm64/x64)
3. ~/.html_to_markdown_ffi/ cache (populated by downloadIfNeeded())
4. A checked-out Cargo workspace's target/release/ (development)
5. Platform default name (DynamicLibrary.open(libName) — Android jniLibs)
6. DynamicLibrary.process() / executable() (iOS static link)

NativeLibrary.downloadIfNeeded() short-circuits when a bundled binary is present and is otherwise only needed on platforms without bundled artifacts (Linux, Windows).

API Reference

Functions

• convert(String html, {ConversionOptions? options, Visitor? visitor}) → ConversionResult

Classes

• ConversionOptions — 40+ configuration fields
• ConversionResult — Output with content, metadata, tables, images, warnings
• HtmlMetadata — Extracted page metadata
• Visitor — Abstract class with 38 element-level callbacks
• NodeContext — Context passed to visitor callbacks

Enums

HeadingStyle, LinkStyle, CodeBlockStyle, WhitespaceMode, OutputFormat, NewlineStyle, HighlightStyle, ListIndentType, PreprocessingPreset, VisitResult, NodeType, WarningKind

Exceptions

HtmlToMarkdownException, InvalidInputException, ConversionErrorException

Development

Prebuilt binaries for the supported platforms ship with the package (native/), so tests and examples run out of the box. To rebuild the native library (libhtml_to_markdown_ffi) from source instead, use the Rust repo:

git clone https://github.com/arrrrny/html-to-markdown.git
cd html-to-markdown/crates/html-to-markdown-ffi
cargo build --release

Run tests

dart pub get dart test

Related

• Rust core
• kreuzberg — Document intelligence framework
• All language bindings