Ladybird

What it is

Ladybird is a web browser with its own engine, built on web standards. Its README calls it a truly independent web browser in a pre-alpha state, only suitable for developers. The FAQ says it is not a Chromium shell, not a WebKit port and not a Firefox fork. Many core libraries are inherited from SerenityOS, and the FAQ names Harfbuzz, Skia, simdutf and libcurl among its third-party ones. This entry is about building and running it, since there is no installer to download.

1. Install the build packages for your system
2. Clone the repository
3. Run ./Meta/ladybird.py run in the clone
4. The script builds a Release version and starts it
5. Try sites and file a reduced test case for what breaks

Who it suits

Developers who want to try a new browser engine, read its code or test their sites in it. The README says it is only suitable for developers today. The FAQ roadmap lists an alpha for developers and early adopters on Linux and macOS in 2026, so today you build it rather than install it.

Skip it if you need a daily browser. The README says it is only suitable for developers, and the FAQ says you have to build it from source to try it.

Where to use it

The README says Ladybird runs on Linux, macOS, Windows with WSL2 and many other Unix-like systems. The build page gives steps for Linux, macOS, Windows, FreeBSD and Android.

• Linux: Debian and Ubuntu, Arch and Manjaro, Fedora, openSUSE and Void, each with its own package line, and a Nix development shell kept in the nix-environments repository
• macOS: Xcode 15, or clang from Homebrew
• Windows: WSL2 is the supported route, and a native Clang-CL build is experimental
• FreeBSD: a package line on the build page
• Android: Android Studio, or Gradle in UI/Android

Ladybird is built with one of two frontends. Android has its own Android UI, and every other platform uses Qt.

How to set it up

Get it saves a zip of Mindket’s setup notes in your downloads folder, with each platform’s steps from the Ladybird build page. The main route is one script, Meta/ladybird.py, once your system’s packages are installed.

1. Install your system’s packages. The kit’s setup notes carry the package lines the build page gives.
2. Clone the repository and go into it.
3. Run the script. It builds a Release version of Ladybird, with its dependencies, and starts it.
4. For a Debug version, set BUILD_PRESET to Debug before the same command.

git clone https://github.com/LadybirdBrowser/ladybird.git
cd ladybird
./Meta/ladybird.py run

BUILD_PRESET=Debug ./Meta/ladybird.py run

On macOS with clang from Homebrew, the build page gives this form:

CC=$(brew --prefix llvm)/bin/clang CXX=$(brew --prefix llvm)/bin/clang++ ./Meta/ladybird.py run

For the experimental Clang-CL build on Windows, the build page installs pkg-config for the vcpkg install with Chocolatey, then builds in a VS command prompt:

choco install pkgconfiglite -y
py Meta\ladybird.py build

How to use it

Once the build is done, the run command starts Ladybird. The same script has a few other commands.

Put --no-build before the executable name. Anything after the name goes to the executable.

./Meta/ladybird.py run --no-build js --evaluate 'console.log(1 + 1)'

Example

A page looks wrong in Ladybird and fine in another browser. You save it as REDUCTION.html, open that file in Ladybird and check that the same problem happens. Then you cut the file down and reload after each cut. First turn scripting off in Ladybird’s Debug menu to see whether a script causes it. Then remove CSS rules and elements one at a time.

If the page did not come from a SingleFile copy, ISSUES.md says to put a base element into the document, like this, so relative images, style sheets and scripts load:

<base href="https://ladybird.org/">

The smallest file that still shows the problem goes up on a site such as CodePen, JSBin or JSFiddle. Its URL goes into the bug report form.

For newcomers and experts

If you are new. A browser engine is the part that loads a page and draws it. Ladybird writes its own instead of reusing the one in Chromium, WebKit or Firefox. Building it is the first test. Pick your system’s note, install the packages, and run the script. If the build fails, read the troubleshooting note before you ask. The project wants build problems in the build-problems channel on its Discord, not in GitHub issues.

For experts. Each tab runs in its own sandboxed WebContent process. Image decoding and network connections run out of process, in ImageDecoder and RequestServer. The code is split into libraries such as LibWeb, LibJS and LibWasm, and it uses the project’s own AK library instead of the C++ STL. The FAQ says features follow the spec algorithms step by step, with the spec text in comments and an AD-HOC: label on code that maps to no spec step.

For packaging, or for several configurations, a custom build directory avoids the script. The build page gives these lines, and a pool size for machines with little memory. Without the script, you may need to give a suitable C++ compiler with the CMAKE_C_COMPILER and CMAKE_CXX_COMPILER options.

cmake --preset Release -B MyBuildDir
cmake --build --preset Release MyBuildDir
ninja -C MyBuildDir run-ladybird

cmake --preset Release -B MyBuildDir -DLAGOM_LINK_POOL_SIZE=2

Good to know

Most of this entry is about a build that runs on your computer. A few things sit outside it.

• Stage: the README says pre-alpha. The FAQ roadmap lists an alpha for Linux and macOS in 2026, a downloadable beta for Linux and macOS in 2027 and a stable release for general use in 2028
• Dependencies: the build manages its third-party dependencies through vcpkg, and a failure in one of them can show up as a Ninja error
• Contributions: CONTRIBUTING.md says only the project maintainers change the code, and it accepts no pull requests from anyone else. Bug reports, reductions and website testing are welcome
• Windows: the FAQ says a native port is not a priority, so WSL2 is the way
• Troubleshooting: one fix edits /etc/ssl/openssl.cnf for the whole system, so read it before you apply it
• Money: the FAQ says the project is funded entirely by donations and sponsorships, and takes no default search deals or other user monetization
• Not an endorsement: Mindket wrote these notes, and the Ladybird project did not make or endorse them
• License: BSD 2-Clause, with the copyright held by the Ladybird developers