Ladybird is a web browser developed from scratch with the goal of being truly independent—free from reliance on existing browser engines like Chromium or Gecko. It is designed for developers and technical users who value transparency, security, and control over their browsing environment. Built as part of the SerenityOS ecosystem, Ladybird leverages a suite of custom-built libraries to implement core web technologies: rendering, JavaScript execution, WebAssembly, networking, and media playback—all in a multi-process architecture. This approach isolates tabs and critical subsystems to improve stability and reduce attack surface.
Although currently in pre-alpha, Ladybird is not a prototype but an ambitious engineering effort to reimagine the browser stack with modern safety and modularity in mind. It supports Linux, macOS, Windows (via WSL2), and other *NIX systems, making it accessible to a wide range of developers who want to explore or contribute to a completely open and auditable browser implementation.
What You Get
- Multi-process architecture - Ladybird separates the UI, rendering, image decoding, and network layers into distinct processes to isolate crashes and malicious content, improving overall stability and security.
- Sandboxed tab rendering - Each tab runs in its own renderer process, preventing one compromised website from affecting others or the host system.
- Custom web stack built on SerenityOS - Ladybird uses LibWeb (rendering), LibJS (JavaScript), LibWasm (WebAssembly), LibTLS (secure connections), and other SerenityOS libraries, ensuring full control over the stack without third-party dependencies.
- Cross-platform support - Can be built and run on Linux, macOS, Windows (via WSL2), and other Unix-like systems with standard build toolchains.
- Transparent, auditable codebase - Entire browser stack is open source under a 2-clause BSD license, enabling deep inspection and modification by developers.
Common Use Cases
- Building a secure, auditable browser extension - Developers can extend Ladybird’s LibWeb or LibJS components to implement custom features without relying on Chromium’s V8 or Blink internals.
- Researching web engine architecture - Academic researchers and systems engineers use Ladybird to study modern browser design without the complexity of Chromium’s massive codebase.
- Problem → Solution flow: Avoiding vendor lock-in in web browsers - Users tired of Chromium dominance and privacy concerns use Ladybird to test an alternative browser engine that is lightweight, transparent, and designed for security by default.
- Team/workflow scenario: Open-source browser contributors - Developers from diverse backgrounds collaborate on Ladybird’s Discord server to implement new web standards, fix rendering bugs, or improve performance—all using standardized C++ and SerenityOS libraries.
Under The Hood
The Ladybird browser project is a modern, standards-compliant browser engine built from the ground up with a focus on performance, safety, and extensibility. It leverages a modular C++ architecture to deliver a clean systems-level implementation that supports cross-platform functionality and integrates seamlessly with web technologies.
Architecture
This project follows a well-structured, layered architecture that emphasizes modularity and resource safety. The system is built around a foundational utilities library (AK) that provides core abstractions and data structures.
- The architecture is built on a core utilities library (AK) that supplies essential system-level tools and memory management primitives
- Design patterns like RAII, intrusive containers, and smart pointer usage are consistently applied for safe and efficient resource handling
- Components interact through well-defined interfaces with minimal coupling, supporting extensibility and maintainability
- Cross-platform support is achieved through conditional compilation and platform-specific implementations, ensuring abstraction at multiple layers
Tech Stack
The project is primarily implemented in C++ with supporting web technologies and modern development practices.
- Built predominantly in C++, incorporating HTML, JavaScript, and Swift for web rendering and UI integration
- Relies heavily on custom utility libraries such as AK, alongside standard C++ features like smart pointers and concurrency primitives
- Uses CMake for build management and includes linting and formatting configurations via Ruff and clang-tidy
- Features an extensive test suite that demonstrates a strong commitment to automated validation and quality assurance
Code Quality
This codebase reflects a mature approach to systems programming with an emphasis on correctness and performance.
- Comprehensive test coverage and structured error handling through try/catch and explicit propagation mechanisms
- Strong adherence to naming conventions and modular design principles, ensuring code clarity and consistency
- Memory safety is prioritized through atomic reference counting and copy-on-write patterns
- Some legacy constructs and workaround patterns indicate areas of technical debt that could be refined
What Makes It Unique
Ladybird distinguishes itself through innovative use of systems programming techniques and a clean, extensible architecture.
- Extensive use of intrusive data structures (e.g., IntrusiveList, IntrusiveRedBlackTree) for zero-overhead memory management and high-performance operations
- A strong focus on memory safety with atomic reference counting, copy-on-write patterns, and safe smart pointer abstractions
- Modular design that cleanly separates core engine logic from platform-specific implementations, enabling robust cross-platform support
- Integration of Swift and C++ through a unified type system and shared memory models for enhanced developer productivity