There are instructions for other platforms linked from the get the code page.
Are you a Google employee? See go/building-chrome-win instead.
Chromium requires Visual Studio 2022 (>=17.0.0) to build. Visual Studio can also be used to debug Chromium. The clang-cl compiler is used but Visual Studio's header files, libraries, and some tools are required. Visual Studio Community Edition should work if its license is appropriate for you. You must install the “Desktop development with C++” component and the “MFC/ATL support” sub-components. This can be done from the command line by passing these arguments to the Visual Studio installer (see below for ARM64 instructions):
$ PATH_TO_INSTALLER.EXE ^ --add Microsoft.VisualStudio.Workload.NativeDesktop ^ --add Microsoft.VisualStudio.Component.VC.ATLMFC ^ --includeRecommended
If you want to build for ARM64 Win32 then some extra arguments are needed. The full set for that case is:
$ PATH_TO_INSTALLER.EXE ^ --add Microsoft.VisualStudio.Workload.NativeDesktop ^ --add Microsoft.VisualStudio.Component.VC.ATLMFC ^ --add Microsoft.VisualStudio.Component.VC.Tools.ARM64 ^ --add Microsoft.VisualStudio.Component.VC.MFC.ARM64 ^ --includeRecommended
Required
depot_toolsDownload the depot_tools bundle and extract it somewhere (eg: C:\src\depot_tools).
Warning: DO NOT use drag-n-drop or copy-n-paste extract from Explorer, this will not extract the hidden “.git” folder which is necessary for depot_tools to autoupdate itself. You can use “Extract all…” from the context menu though.
Add depot_tools to the start of your PATH (must be ahead of any installs of Python. Note that environment variable names are case insensitive).
C:\src\depot_tools at the front (or at least in front of any directory that might already have a copy of Python or Git).C:\src\depot_tools at the front. Note: If your system PATH has a Python in it, you will be out of luck.Also, add a DEPOT_TOOLS_WIN_TOOLCHAIN environment variable in the same way, and set it to 0. This tells depot_tools to use your locally installed version of Visual Studio (by default, depot_tools will try to use a google-internal version).
You may also have to set variable vs2022_install to your installation path of Visual Studio 2022, like set vs2022_install=C:\Program Files\Microsoft Visual Studio\2022\Professional.
From a cmd.exe shell, run:
$ gclient
On first run, gclient will install all the Windows-specific bits needed to work with the code, including msysgit and python.
After running gclient open a command prompt and type where python3 and confirm that the depot_tools python3.bat comes ahead of any copies of python3.exe. Failing to ensure this can lead to overbuilding when using gn - see crbug.com/611087.
App Execution Aliases can conflict with other installations of python on the system so disable these for ‘python.exe’ and ‘python3.exe’ by opening ‘App execution aliases’ section of Control Panel and unticking the boxes next to both of these that point to ‘App Installer’.
First, configure Git:
$ git config --global user.name "My Name" $ git config --global user.email "my-name@chromium.org" $ git config --global core.autocrlf false $ git config --global core.filemode false $ git config --global branch.autosetuprebase always
While not necessarily required it can be helpful to configure git to allow long path support (beyond the Windows MAX_PATH limit):
git config --global core.longpaths true
Create a chromium directory for the checkout and change to it. You can call this whatever you like and put it wherever you like, as long as the full path has no spaces. However there are some performance benefits for Googlers in placing the directory under C:\src\ (See Why is my build slow?).
$ mkdir chromium && cd chromium
Run the fetch tool from depot_tools to check out the code and its dependencies.
$ fetch chromium
If you don't want the full repo history, you can save a lot of time by adding the --no-history flag to fetch.
Expect the command to take over an hour on even a fast connection, and many hours on slower ones. You should configure your PC so that it doesn't sleep or hibernate during the fetch or else errors may occur. If errors occur while fetching sub-repos then you can start over, or you may be able to correct them by going to the chromium/src directory and running this command:
$ gclient sync
When fetch completes, it will have created a hidden .gclient file and a directory called src in the working directory. The remaining instructions assume you have switched to the src directory:
$ cd src
Optional: You can also install API keys if you want your build to talk to some Google services, but this is not necessary for most development and testing purposes.
Chromium uses Ninja as its main build tool along with a tool called GN to generate .ninja files. You can create any number of build directories with different configurations. To create a build directory:
$ gn gen out\Default
Default with another name, but it should be a subdirectory of out.gn help on the command line or read the quick start guide.There are some gn flags that can improve build speeds. You can specify these in the editor that appears when you create your output directory (gn args out\Default) or on the gn gen command line (gn gen out\Default --args="is_component_build = true is_debug = true"). Some helpful settings to consider using include:
is_component_build = true - this uses more, smaller DLLs, and may avoid having to relink chrome.dll after every change.enable_nacl = false - this disables Native Client which is usually not needed for local builds.target_cpu = "x86" - x86 builds may be slightly faster than x64 builds. Note that if you set this but don't set enable_nacl = false then build times may get worse.blink_symbol_level = 0 - turn off source-level debugging for blink to reduce build times, appropriate if you don't plan to debug blink.v8_symbol_level = 0 - turn off source-level debugging for v8 to reduce build times, appropriate if you don't plan to debug v8.In order to speed up linking you can set symbol_level = 1 or symbol_level = 0 - these options reduce the work the compiler and linker have to do. With symbol_level = 1 the compiler emits file name and line number information so you can still do source-level debugging but there will be no local variable or type information. With symbol_level = 0 there is no source-level debugging but call stacks still have function names. Changing symbol_level requires recompiling everything.
When invoking ninja, specify ‘chrome’ as the target to avoid building all test binaries as well.
In addition, Google employees should use Reclient, a distributed compilation system. Detailed information is available internally but the relevant gn arg is:
use_remoteexec = trueGoogle employees can visit go/building-chrome-win#setup-remote-execution for more information. For external contributors, Reclient does not support Windows builds.
You might be able to use sccache for the build process by enabling the following arguments:
cc_wrapper = "sccache" - assuming the sccache binary is in your %PATH%chrome_pgo_phase = 0Many things can make builds slow, with Windows Defender slowing process startups being a frequent culprit. Have you ensured that the entire Chromium src directory is excluded from antivirus scanning (on Google machines this means putting it in a src directory in the root of a drive)? Have you tried the different settings listed above, including different link settings and -j values? Have you asked on the chromium-dev mailing list to see if your build is slower than expected for your machine's specifications?
If you suspect that Defender is slowing your build then you can try Microsoft's Performance analyzer for Microsoft Defender Antivirus to investigate in detail.
The next step is to gather some data. If you set the NINJA_SUMMARIZE_BUILD environment variable to 1 then autoninja will do three things. First, it will set the NINJA_STATUS environment variable so that ninja will print additional information while building Chrome. It will show how many build processes are running at any given time, how many build steps have completed, how many build steps have completed per second, and how long the build has been running, as shown here:
$ set NINJA_SUMMARIZE_BUILD=1 $ autoninja -C out\Default base ninja: Entering directory `out\Default' [1 processes, 86/86 @ 2.7/s : 31.785s ] LINK(DLL) base.dll base.dll.lib base.dll.pdb
This makes slow process creation immediately obvious and lets you tell quickly if a build is running more slowly than normal.
In addition, setting NINJA_SUMMARIZE_BUILD=1 tells autoninja to print a build performance summary when the build completes, showing the slowest build steps and slowest build-step types, as shown here:
$ set NINJA_SUMMARIZE_BUILD=1 $ autoninja -C out\Default base Longest build steps: 0.1 weighted s to build obj/base/base/trace_log.obj (6.7 s elapsed time) 0.2 weighted s to build nasm.exe, nasm.exe.pdb (0.2 s elapsed time) 0.3 weighted s to build obj/base/base/win_util.obj (12.4 s elapsed time) 1.2 weighted s to build base.dll, base.dll.lib (1.2 s elapsed time) Time by build-step type: 0.0 s weighted time to generate 6 .lib files (0.3 s elapsed time sum) 0.1 s weighted time to generate 25 .stamp files (1.2 s elapsed time sum) 0.2 s weighted time to generate 20 .o files (2.8 s elapsed time sum) 1.7 s weighted time to generate 4 PEFile (linking) files (2.0 s elapsed time sum) 23.9 s weighted time to generate 770 .obj files (974.8 s elapsed time sum) 26.1 s weighted time (982.9 s elapsed time sum, 37.7x parallelism) 839 build steps completed, average of 32.17/s
The “weighted” time is the elapsed time of each build step divided by the number of tasks that were running in parallel. This makes it an excellent approximation of how “important” a slow step was. A link that is entirely or mostly serialized will have a weighted time that is the same or similar to its elapsed time. A compile that runs in parallel with 999 other compiles will have a weighted time that is tiny.
You can also generate these reports by manually running the script after a build:
$ python depot_tools\post_build_ninja_summary.py -C out\Default
Finally, setting NINJA_SUMMARIZE_BUILD=1 tells autoninja to tell Ninja to report on its own overhead by passing “-d stats”. This can be helpful if, for instance, process creation (which shows up in the StartEdge metric) is making builds slow, perhaps due to antivirus interference due to clang-cl not being in an excluded directory:
$ set NINJA_SUMMARIZE_BUILD=1 $ autoninja -C out\Default base metric count avg (us) total (ms) .ninja parse 3555 1539.4 5472.6 canonicalize str 1383032 0.0 12.7 canonicalize path 1402349 0.0 11.2 lookup node 1398245 0.0 8.1 .ninja_log load 2 118.0 0.2 .ninja_deps load 2 67.5 0.1 node stat 2516 29.6 74.4 depfile load 2 1132.0 2.3 StartEdge 88 3508.1 308.7 FinishCommand 87 1670.9 145.4 CLParser::Parse 45 1889.1 85.0
You can also get a visual report of the build performance with ninjatracing. This converts the .ninja_log file into a .json file which can be loaded into chrome://tracing:
$ python ninjatracing out\Default\.ninja_log >build.json
Build Chromium (the “chrome” target) with Ninja using the command:
$ autoninja -C out\Default chrome
autoninja is a wrapper that automatically provides optimal values for the arguments passed to ninja.
You can get a list of all of the other build targets from GN by running gn ls out\Default from the command line. To compile one, pass to Ninja the GN label with no preceding “//” (so for //chrome/test:unit_tests use autoninja -C out\Default chrome/test:unit_tests).
Ninja supports a special syntax ^ to compile a single object file specyfing the source file. For example, ninja -C out/Default ../../base/logging.cc^ compiles obj/base/base/logging.o.
With autoninja, you need to add ^^ to preserve the trailing ^.
$ autoninja -C out\Default ..\..\base\logging.cc^^
In addition to foo.cc^^, Siso also supports foo.h^^ syntax to compile the corresponding foo.o if it exists.
Once it is built, you can simply run the browser:
$ out\Default\chrome.exe
(The “.exe” suffix in the command is actually optional).
Tests are split into multiple test targets based on their type and where they exist in the directory structure. To see what target a given unit test or browser test file corresponds to, the following command can be used:
$ gn refs out\Default --testonly=true --type=executable --all chrome\browser\ui\browser_list_unittest.cc //chrome/test:unit_tests
In the example above, the target is unit_tests. The unit_tests binary can be built by running the following command:
$ autoninja -C out\Default unit_tests
You can run the tests by running the unit_tests binary. You can also limit which tests are run using the --gtest_filter arg, e.g.:
$ out\Default\unit_tests.exe --gtest_filter="BrowserListUnitTest.*"
You can find out more about GoogleTest at its GitHub page.
To update an existing checkout, you can run
$ git rebase-update $ gclient sync -D
The first command updates the primary Chromium source repository and rebases any of your local branches on top of tip-of-tree (aka the Git branch origin/main). If you don't want to use this script, you can also just use git pull or other common Git commands to update the repo.
The second command syncs the subrepositories to the appropriate versions, deleting those that are no longer needed, and re-runs the hooks as needed.
You can use the Visual Studio IDE to edit and debug Chrome, with or without Intellisense support.
If you want to use Visual Studio Intellisense when developing Chromium, use the --ide command line argument to gn gen when you generate your output directory (as described on the get the code page). This is an example when your checkout is C:\src\chromium and your output directory is out\Default:
$ gn gen --ide=vs --ninja-executable=C:\src\chromium\src\third_party\ninja\ninja.exe out\Default $ devenv out\Default\all.sln
GN will produce a file all.sln in your build directory. It will internally use Ninja to compile while still allowing most IDE functions to work (there is no native Visual Studio compilation mode). If you manually run “gen” again you will need to resupply this argument, but normally GN will keep the build and IDE files up to date automatically when you build.
The generated solution will contain several thousand projects and will be very slow to load. Use the --filters argument to restrict generating project files for only the code you're interested in. Although this will also limit what files appear in the project explorer, debugging will still work and you can set breakpoints in files that you open manually. A minimal solution that will let you compile and run Chrome in the IDE but will not show any source files is:
$ gn gen --ide=vs --ninja-executable=C:\src\chromium\src\third_party\ninja\ninja.exe --filters=//chrome --no-deps out\Default
You can selectively add other directories you care about to the filter like so: --filters=//chrome;//third_party/WebKit/*;//gpu/*.
There are other options for controlling how the solution is generated, run gn help gen for the current documentation.
It is also possible to debug and develop Chrome in Visual Studio without the overhead of a multi-project solution file. Simply “open” your chrome.exe binary with File->Open->Project/Solution, or from a Visual Studio command prompt like so: devenv /debugexe out\Debug\chrome.exe <your arguments>. Many of Visual Studio's code exploration features will not work in this configuration, but by installing the VsChromium Visual Studio Extension you can get the source code to appear in the solution explorer window along with other useful features such as code search. You can add multiple executables of interest (base_unittests.exe, browser_tests.exe) to your solution with File->Add->Existing Project... and change which one will be debugged by right-clicking on them in Solution Explorer and selecting Set as Startup Project. You can also change their properties, including command line arguments, by right-clicking on them in Solution Explorer and selecting Properties.
By default when you start debugging in Visual Studio the debugger will only attach to the main browser process. To debug all of Chrome, install Microsoft's Child Process Debugging Power Tool. You will also need to run Visual Studio as administrator, or it will silently fail to attach to some of Chrome's child processes.
Try running
$ git update-index --test-untracked-cache
If the output ends with OK, then the following may also improve performance of git status:
$ git config core.untrackedCache true
You can significantly speed up git by using fsmonitor. You should enable fsmonitor in large repos, such as Chromium and v8. Enabling it globally will launch many processes and consume excess commit/memory and probably isn't worthwhile. The command to enable fsmonitor in the current repo is:
$ git config core.fsmonitor true