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Windows port

WebKit had two Windows ports, Apple Windows port and WinCairo port. WinCairo port is called Windows port after the Apple Windows port was deprecated. It is using cairo for the graphics backend, libcurl for the network backend. It supports only 64 bit Windows.

Installing Development Tools

Install the latest Visual Studio with "Desktop development with C++" workload.

Install CMake, Perl, Python, Ruby, gperf (GnuWin32 Gperf), LLVM, and Ninja. Python 3.12 has a problem for WebKit at the moment. Use Python 3.11.

You can use Chocolatey to install the tools. ActivePerl chocolatey package has a problem and no package maintainer now. XAMPP includes Perl, and running layout tests needs XAMPP. Install XAMPP instead.

choco install -y xampp-81 python311 ruby git cmake gperf llvm ninja

Install pywin32 Python module for run-webkit-tests and git-webkit.

python -m pip install pywin32

Windows Git enables autocrlf by default. But, some layout tests files have to be checked out as LF line end style. See Bug 240158.

git config --global core.autocrlf input

Using WinGet

If you prefer WinGet to Chocolatey, you can use it. Invoke the following command in an elevated PowerShell or cmd prompt.

winget install --scope=machine --id Git.Git Kitware.CMake Ninja-build.Ninja Python.Python.3.11 RubyInstallerTeam.Ruby.3.2 ApacheFriends.Xampp.8.2 LLVM.LLVM
winget install --id GnuWin32.Gperf

If --scope=machine isn't specified, Python is installed under your user profile directory.

WinGet may not append the path into your PC. If some errors occered, please check your path settings, including LLVM and GnuWin32(Gperf).

WebKit command prompt

To compile, run programs and run tests, you need to set some environment variables. For ease of development, it's recommended to create a batch file to set environment variables and open PowerShell. Create a batch file with the following content with adjusting it to your PC. And put it in the top WebKit source directory. And double-click it to open PowerShell, we call this opened shell as "WebKit command prompt" hereafter.

@echo off
cd %~dp0

path C:\xampp\apache\bin;%path%
path C:\xampp\perl\bin;%path%
path %ProgramFiles%\CMake\bin;%path%
path %ProgramFiles(x86)%\Microsoft Visual Studio\Installer;%path%
for /F "usebackq delims=" %%I in (`vswhere.exe -latest -property installationPath`) do set VSPATH=%%I

rem set WEBKIT_LIBRARIES=%~dp0WebKitLibraries\win
path %~dp0WebKitLibraries\win\bin64;%path%
set WEBKIT_TESTFONTS=%~dp0Tools\WebKitTestRunner\fonts

set CC=clang-cl
set CXX=clang-cl

rem set http_proxy=http://your-proxy:8080
rem set https_proxy=%http_proxy%

rem You can pass necessary JSC options
rem set JSC_dumpOptions=1
rem set JSC_useJIT=0
rem set JSC_useDFGJIT=0
rem set JSC_useRegExpJIT=0
rem set JSC_useDOMJIT=0

rem You can show check TextureMapper FPS via WEBKIT_SHOW_FPS.

call "%VSPATH%\VC\Auxiliary\Build\vcvars64.bat"
cd %~dp0
start powershell

You can replace powershell with cmd or wt (Windows Terminal) if you like.


In the WebKit command prompt, invoke build-webkit to start building.

perl Tools/Scripts/build-webkit --release

You will get required libraries WebKitRequirements downloaded automatically when you perform a build-webkit. It checks the latest WebKitRequirements every time. I'd like to recommend to use --skip-library-update for incremental build to speed up for the next time.

python Tools\Scripts\
perl Tools\Scripts\build-webkit --release --skip-library-update

The build succeeded if you got WebKit is now built message. Run your MiniBrowser.


You can run programs under a debugger with this instruction.

Building from within Visual Studio

You can use CMake Visual Studio generator instead of Ninja generator. Install the LLVM extension of MSBuild.

In the WebKit command prompt,

perl Tools/Scripts/build-webkit --release --no-ninja --generate-project-only

Open the generated solution file by invoking devenv command from a WebKit command prompt.

devenv WebKitBuild\Release\WebKit.sln

Build "MiniBrowser" project.

Running the tests

WebKit test runner run-webkit-tests is using a command line debugger NTSD to get crash logs. However, Windows SDK installer doesn't install it by default.

  1. Right-click the Windows start menu
  2. Select "Apps and Features" menu item
  3. Click "Windows Software Development Kit" from the apps list
  4. Click "Modify" button
  5. Select "Change" and push "Next" button
  6. Select "Debugging Tools for Windows" and proceed the installation

Install XAMPP as described above.

Install required Python and Ruby modules.

python -m pip install pywin32
gem install webrick

If Apache service is running, stop it.

net stop apache2.4

Some extensions need to be registered as CGI. Modify the following commands for your Perl and Python paths, and run them as administrator.

An example using Chocolatey

reg add HKEY_CLASSES_ROOT\.pl\Shell\ExecCGI\Command /ve /d "c:\xampp\perl\bin\perl.exe -T"
reg add HKEY_CLASSES_ROOT\.cgi\Shell\ExecCGI\Command /ve /d "c:\xampp\perl\bin\perl.exe -T"
reg add HKEY_CLASSES_ROOT\.py\Shell\ExecCGI\Command /ve /d "c:\Python311\python.exe -X utf8"

An example using WinGet

reg add HKEY_CLASSES_ROOT\.pl\Shell\ExecCGI\Command /ve /d "c:\xampp\perl\bin\perl.exe -T"
reg add HKEY_CLASSES_ROOT\.cgi\Shell\ExecCGI\Command /ve /d "c:\xampp\perl\bin\perl.exe -T"
reg add HKEY_CLASSES_ROOT\.py\Shell\ExecCGI\Command /ve /d "\`"C:\Program Files\Python311\python.exe\`" -X utf8"

You need openssl.exe in your PATH to run wpt server. XAMPP contains openssl.exe in C:\xampp\apache\bin directory. Append the directory to your PATH.

Open the WebKit command prompt as administrator because http tests need to run Apache service.

Invoke run-webkit-tests.

python Tools/Scripts/run-webkit-tests --release

If you are using Japanese Windows, some layout tests fail due to form control size differences. GetStockObject(DEFAULT_GUI_FONT) returns MS UI Gothic on it. Remove GUIFont.Facename of HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\GRE_Initialize. And, replace MS UI Gothic with Microsoft Sans Serif in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontSubstitutes\MS Shell Dlg. Also, change system locale to English, because Python script crashes non-English system locale. See Bug 273060.

If http tests fail as flaky failures due to the socket count limit, increase the user port range. See Bug 224523

netsh int ipv4 set dynamicport tcp start=1025 num=64511

Running the tests in Docker

You can use Docker to run LayoutTests by mounting the host directory.

docker run -it --rm --cpu-count=8 --memory=16g -v %cd%:c:\repo -w c:\repo webkitdev/msbuild

Downloading build artifacts from Buildbot