Installing Bazel on Windows

Installing

Step 1: Check your system

Recommended: 64 bit Windows 10, version 1703 (Creators Update) or newer, enable “Developer Mode”.

Also supported:

  • 64 bit Windows 7 or newer

  • 64 bit Windows Server 2008 R2 or newer

  • Older Windows 10 versions, disabled “Developer Mode” (enabling the mode just lets you use the --enable_runfiles Bazel flag)

Step 2: Install the prerequisites

Step 3: Download Bazel

Download the Bazel binary (bazel-<version>-windows-x86_64.exe) from GitHub.

Recommended: rename this binary to bazel.exe and move it to a directory on the PATH.

Alternatively you can:

Step 4 (optional): Configure output directories

You can skip this step. Bazel can work without configuring the output directories, and will use its default values.

By default, Bazel writes to two directories:

  • The “output user root”, configurable with the --output_user_root flag.

    This is where Bazel extracts from itself its embedded tools, its own runtime, and where it writes some log files and some caches.

    This is also the default location for the “output base”.

  • The “output base”, configurable with the --output_base flag.

    This is where Bazel writes all output files. By default, this is a subdirectory of the “output user root”.

By default, Bazel also writes in the workspace directory:

  • The “convenience symlinks”, configurable with the --symlink_prefix flag.

    These are the “bazel-bin”, “bazel-testlogs”, and similar directories that Bazel creates in your workspace. These are not really directories but “junctions”: they just point to other directories in your filesystem (under the “output root”).

    You can tell Bazel not to create these junctions with --symlink_prefix=/.

Step 5 (optional): Install compilers and language runtimes

You can skip this step. Bazel can work without these programs, but you may need them.

We recommend installing:

  • MSYS2 x86_64

    MSYS2 is a software distro and building platform for Windows. It contains Bash and common Unix tools (like grep, tar, git).

    You will need MSYS2 to build, test, or run targets that depend on Bash. Typically these are genrule, sh_binary, sh_test, but there may be more (e.g. Starlark rules). Bazel shows an error if a build target needs Bash but Bazel could not locate it.

  • Common MSYS2 packages

    You will likely need these to build and run targets that depend on Bash. MSYS2 does not install these tools by default, so you need to install them manually. Projects that depend on Bash tools in PATH need this step (for example TensorFlow).

    Open the MSYS2 terminal and run this command:

    pacman -S zip unzip patch diffutils git

    Optional: If you want to use Bazel from CMD or Powershell and still be able to use Bash tools, make sure to add MSYS2_INSTALL_PATH/usr/bin to your PATH environment variable.

  • Build Tools for Visual Studio 2019

    Make sure you install the C++ build tools with the Windows 10 SDK.

    You will need this to build C++ code on Windows.

    Also supported:

    • Visual Studio 2015 (or newer) with Visual C++ and Windows 10 SDK

    • Visual C++ Build Tools 2015 (or newer) and Windows 10 SDK

  • Java SE Development Kit 10 (JDK) for Windows x64

    You will need this to build Java code on Windows.

    Also supported: Java 8 and 9

  • Python 2.7 for Windows x86-64

    You will need this to build Python code on Windows.

    Also supported: Python 3 or newer for Windows x86-64

Step 6: Done

You have successfully installed Bazel.

Troubleshooting: see troubleshooting below.

Tutorials: see Getting Started with Bazel > Tutorials.

Troubleshooting

Bazel does not find Bash or bash.exe

Possible reasons:

  • you installed MSYS2 not under the default install path

  • you installed MSYS2 i686 instead of MSYS2 x86_64

  • you installed MSYS instead of MSYS2

Solution:

Ensure you installed MSYS2 x86_64.

If that doesn’t help:

  1. Go to Start Menu > Settings.

  2. Find the setting “Edit environment variables for your account”

  3. Look at the list on the top (“User variables for <username>”), and click the “New…” button below it.

  4. For “Variable name”, enter BAZEL_SH

  5. Click “Browse File…”

  6. Navigate to the MSYS2 directory, then to usr\bin below it.

    For example, this might be C:\msys64\usr\bin on your system.

  7. Select the bash.exe or bash file and click OK

  8. The “Variable value” field now has the path to bash.exe. Click OK to close the window.

  9. Done.

    If you open a new cmd.exe or PowerShell terminal and run Bazel now, it will find Bash.

Bazel does not find Visual Studio or Visual C++

Possible reasons:

  • you installed multiple versions of Visual Studio

  • you installed and removed various versions of Visual Studio

  • you installed various versions of the Windows SDK

  • you installed Visual Studio not under the default install path

Solution:

  1. Go to Start Menu > Settings.

  2. Find the setting “Edit environment variables for your account”

  3. Look at the list on the top (“User variables for <username>”), and click the “New…” button below it.

  4. For “Variable name”, enter BAZEL_VC

  5. Click “Browse Directory…”

  6. Navigate to the VC directory of Visual Studio.

    For example, this might be C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC on your system.

  7. Select the VC folder and click OK

  8. The “Variable value” field now has the path to VC. Click OK to close the window.

  9. Done.

    If you open a new cmd.exe or PowerShell terminal and run Bazel now, it will find Visual C++.

Other ways to install Bazel

Using Chocolatey

  1. Install the Chocolatey package manager

  2. Install the Bazel package:

    choco install bazel

    This command will install the latest available version of Bazel and its dependencies, such as the MSYS2 shell. This will not install Visual C++ though.

See Chocolatey installation and package maintenance guide for more information about the Chocolatey package.

Using Scoop

  1. Install the Scoop package manager using the following PowerShell command:

    iex (new-object net.webclient).downloadstring('https://get.scoop.sh')

  2. Install the Bazel package:

    scoop install bazel

See Scoop installation and package maintenance guide for more information about the Scoop package.

Build from source

See here.