# Checking out and Building Chromium for Windows

There are instructions for other platforms linked from the 
[get the code](get_the_code.md) page.

## Instructions for Google Employees

Are you a Google employee? See
[go/building-chrome-win](https://goto.google.com/building-chrome-win) instead.

[TOC]

## System requirements

* A 64-bit Intel machine with at least 8GB of RAM. More than 16GB is highly
  recommended.
* At least 100GB of free disk space on an NTFS-formatted hard drive. FAT32
  will not work, as some of the Git packfiles are larger than 4GB.
* Visual Studio 2015 Update 3, see below (no other version is supported).
* Windows 7 or newer.

## Setting up Windows

### Visual Studio

As of December 8, 2016 Chromium requires Visual Studio 2015, with the 14393
Windows SDK to build.

Install Visual Studio 2015 Update 3 or later - Community Edition
should work if its license is appropriate for you. Use the Custom Install option
and select:

- Visual C++, which will select three sub-categories including MFC
- Universal Windows Apps Development Tools > Tools (1.4.1) and Windows 10 SDK
  (10.0.14393)

You must have the 14393 SDK installed or else you will hit compile errors such
as undefined or redefined macros.

Install the Windows SDK 10, and choose Debugging Tools For Windows when you
install this in order to get windbg.

## Install `depot_tools`

Download the [depot_tools bundle](https://storage.googleapis.com/chrome-infra/depot_tools.zip)
and extract it somewhere.

*** note
**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). Assuming you unzipped the bundle to C:\src\depot_tools, open:

Control Panel → System and Security → System → Advanced system settings

If you have Administrator access, Modify the PATH system variable and
put `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).

If you don't have Administrator access, you can add a user-level PATH
environment variable and put `C:\src\depot_tools` at the front, but
if your system PATH has a Python in it, you will be out of luck.

Also, add a DEPOT_TOOLS_WIN_TOOLCHAIN system 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).

From a cmd.exe shell, run the command gclient (without arguments). On first
run, gclient will install all the Windows-specific bits needed to work with
the code, including msysgit and python.

* If you run gclient from a non-cmd shell (e.g., cygwin, PowerShell),
  it may appear to run properly, but msysgit, python, and other tools
  may not get installed correctly.
* If you see strange errors with the file system on the first run of gclient,
  you may want to [disable Windows Indexing](http://tortoisesvn.tigris.org/faq.html#cantmove2).

After running gclient open a command prompt and type `where python` and 
confirm that the depot_tools `python.bat` comes ahead of any copies of 
python.exe. Failing to ensure this can lead to overbuilding when 
using gn - see [crbug.com/611087](https://crbug.com/611087).

## Get the code

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):

```shell
$ mkdir chromium && cd chromium
```

Run the `fetch` tool from `depot_tools` to check out the code and its
dependencies.

```shell
$ 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 30 minutes on even a fast connection, and many
hours on slower ones.

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:

```shell
$ cd src
```

*Optional*: You can also [install API
keys](https://www.chromium.org/developers/how-tos/api-keys) if you want your
build to talk to some Google services, but this is not necessary for most
development and testing purposes.

## Setting up the build

Chromium uses [Ninja](https://ninja-build.org) as its main build tool along
with a tool called [GN](../tools/gn/docs/quick_start.md) to generate `.ninja`
files. You can create any number of *build directories* with different
configurations. To create a build directory:

```shell
$ gn gen out/Default
```

* You only have to run this once for each new build directory, Ninja will
  update the build files as needed.
* You can replace `Default` with another name, but
  it should be a subdirectory of `out`.
* For other build arguments, including release settings, see [GN build
  configuration](https://www.chromium.org/developers/gn-build-configuration).
  The default will be a debug component build matching the current host
  operating system and CPU.
* For more info on GN, run `gn help` on the command line or read the
  [quick start guide](../tools/gn/docs/quick_start.md).

### Using the Visual Studio IDE

If you want to use the Visual Studio IDE, use the `--ide` command line
argument to `gn gen` when you generate your output directory (as described on
the [get the code](https://dev.chromium.org/developers/how-tos/get-the-code)
page):

```shell
$ gn gen --ide=vs 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. 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 --filters=//chrome out\Default
```

There are other options for controlling how the solution is generated, run `gn
help gen` for the current documentation.

### Faster builds

* Reduce file system overhead by excluding build directories from
  antivirus and indexing software.
* Store the build tree on a fast disk (preferably SSD).

Still, expect build times of 30 minutes to 2 hours when everything has to
be recompiled.

## Build Chromium

Build Chromium (the "chrome" target) with Ninja using the command:

```shell
$ ninja -C out\Default chrome
```

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 ninja -C out/Default chrome/test:unit_tests`).

## Run Chromium

Once it is built, you can simply run the browser:

```shell
$ out\Default\chrome.exe
```

(The ".exe" suffix in the command is actually optional).

## Running test targets

You can run the tests in the same way. You can also limit which tests are
run using the `--gtest_filter` arg, e.g.:

```shell
$ out\Default\unit_tests.exe --gtest_filter="PushClientTest.*"
```

You can find out more about GoogleTest at its
[GitHub page](https://github.com/google/googletest).

## Update your checkout

To update an existing checkout, you can run

```shell
$ git rebase-update
$ gclient sync
```

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/master`).
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 and
re-runs the hooks as needed.