Windows Requirements

Build Requirements

For non-FIPS builds on Windows, the following requirements apply:

* NASM is recommended on x86-64 but can be avoided using prebuilt NASM objects. See the Prebuilt NASM objects section below.

Note: FIPS builds on Windows also require bindgen, as there are no pre-generated FIPS bindings for Windows platforms. See Platform Support for more details.

C/C++ Compiler

Use the following instructions to download Visual Studio Build Tools 2017 or later.

1. Download the Build Tools for Visual Studio installer.
2. Execute the installer.
3. If you have an existing installation chose Modify on the existing installation.
4. Under Workloads select Visual C++ build tools
5. Under Individual components select
   • C++/CLI support
   • C++ CMake tools for Windows
6. For ARM64/aarch64 support, also select:
   • C++ Clang Compiler for Windows
   • MSBuild support for LLVM (clang-cl) toolset
7. Confirm selections and click Install

Alternative: Clang Compiler

As an alternative to MSVC, you can use the Clang compiler on Windows. This can be useful for cross-compilation scenarios or when using MSYS2/MinGW environments. When using Clang:

• Install LLVM/Clang from LLVM releases or via MSYS2
• Ensure clang or clang-cl is available in your PATH
• For MSYS2 environments, the clang64 or ucrt64 subsystems provide Clang toolchains

CMake

CMake is only required for FIPS builds on Windows.

1. Download Windows CMake Installer
2. Execute the installer
3. Add the CMake installation binary directory to your PATH.
   • set PATH="C:\Program Files\CMake\bin;%PATH%"

NASM

NASM is required for x86 and x86-64 builds on Windows.

1. Download and install the Netwide Assembler (NASM)
2. Add the NASM installation directory to your PATH
   • set PATH="C:\Program Files\NASM;%PATH%"

Prebuilt NASM objects

Important: Prebuilt NASM objects are only available for Windows platforms. They are never used on Linux, macOS, or any other platform.

Important: If a NASM assembler is detected in your build environment, it is always used to compile assembly files. Prebuilt NASM objects are only used as a fallback when NASM is not available.

For Windows x86-64 (non-FIPS builds only), you can avoid installing NASM by using prebuilt NASM objects. The build will use prebuilt objects only when all of the following conditions are met:

1. No NASM assembler is found in the build environment
2. The "fips" feature is not enabled
3. The target is x86_64-pc-windows-msvc or x86_64-pc-windows-gnu
4. Either the AWS_LC_SYS_PREBUILT_NASM environment variable is set to 1, or the prebuilt-nasm feature is enabled

To prevent usage of prebuilt NASM objects, install NASM in the build environment and/or set the variable AWS_LC_SYS_PREBUILT_NASM to 0 in the build environment.

About prebuilt NASM objects

Prebuilt NASM objects are generated using automation similar to the crate provided pregenerated bindings. See the repository's GitHub workflow configuration for more information. The prebuilt NASM objects are checked into the repository and are available for inspection. For each PR submitted, CI verifies that the NASM objects newly built from source match the NASM objects currently in the repository.

No-assembly build

It is possible to avoid the NASM requirement by setting the AWS_LC_SYS_NO_ASM/AWS_LC_FIPS_SYS_NO_ASM environment variables. However, this severely impacts performance and can only be used for un-optimized/debug builds. See the notes in our troubleshooting section.

Go

Go is only required for FIPS builds.

1. Download and install Go
2. Add the Go installation binary directory to your PATH
   • set PATH="C:\Program Files\Go\bin;%PATH%"

Ninja

Ninja is only required for FIPS builds on Windows.

1. Download and install Ninja
2. Add the Ninja installation directory to your PATH
   • set PATH="C:\ninja\ninja_build;%PATH%"

Bindgen (FIPS only)

Bindgen is required for FIPS builds on Windows, as there are no pre-generated FIPS bindings for Windows platforms. Using bindgen requires libclang or llvm to be installed. See the requirements page in The bindgen User Guide for instructions.

libclang / LLVM

1. Download LLVM Installer
2. Execute the installer
3. Update your environment to set LIBCLANG_PATH to the bin directory inside LLVM install directory.
   • set LIBCLANG_PATH="C:\Program Files\LLVM\bin"

bindgen-cli

cargo install --force --locked bindgen-cli

FIPS Build Note

Building with the "fips" feature on Windows will result in the creation of shared libraries (named like aws_lc_fips_0_xx_yy_crypto.dll and aws_lc_fips_0_xx_yy_rust_wrapper.dll). These shared libraries will likely need to be distributed alongside any executable that depends on aws-lc-rs.

Troubleshooting

See our troubleshooting section.