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There are various options to build and run OpenSSL on the Windows platforms.
"Native" OpenSSL uses the Windows APIs directly at run time.
To build a native OpenSSL you can either use:
Microsoft Visual C++ (MSVC) C compiler on the command line
MinGW cross compiler
run on the GNU-like development environment MSYS2
or run on Linux or Cygwin
"Hosted" OpenSSL relies on an external POSIX compatibility layer
for building (using GNU/Unix shell, compiler, and tools) and at run time.
For this option you can use Cygwin.
Visual C++ native builds, aka VC-*
Requirement details
In addition to the requirements and instructions listed in,
these are required as well:
- Perl.
We recommend Strawberry Perl, available from
Please read NOTES.PERL for more information, including the use of CPAN.
An alternative is ActiveState Perl,
for which you may need to explicitly build the Perl module Win32/
via and then download it.
- Microsoft Visual C compiler.
Since these are proprietary and ever-changing we cannot test them all.
Older versions may not work. Use a recent version wherever possible.
- Netwide Assembler (NASM), available from
Note that NASM is the only supported assembler.
Quick start
1. Install Perl
2. Install NASM
3. Make sure both Perl and NASM are on your %PATH%
4. Use Visual Studio Developer Command Prompt with administrative privileges,
choosing one of its variants depending on the intended architecture.
Or run "cmd" and execute "vcvarsall.bat" with one of the options x86,
x86_amd64, x86_arm, x86_arm64, amd64, amd64_x86, amd64_arm, or amd64_arm64.
This sets up the environment variables needed for nmake.exe, cl.exe, etc.
See also
5. From the root of the OpenSSL source directory enter
perl Configure VC-WIN32 if you want 32-bit OpenSSL or
perl Configure VC-WIN64A if you want 64-bit OpenSSL or
perl Configure to let Configure figure out the platform
6. nmake
7. nmake test
8. nmake install
For the full installation instructions, or if anything goes wrong at any stage,
check the file.
Installation directories
The default installation directories are derived from environment
For VC-WIN32, the following defaults are use:
PREFIX: %ProgramFiles(86)%\OpenSSL
OPENSSLDIR: %CommonProgramFiles(86)%\SSL
For VC-WIN64, the following defaults are use:
PREFIX: %ProgramW6432%\OpenSSL
OPENSSLDIR: %CommonProgramW6432%\SSL
Should those environment variables not exist (on a pure Win32
installation for examples), these fallbacks are used:
PREFIX: %ProgramFiles%\OpenSSL
OPENSSLDIR: %CommonProgramFiles%\SSL
ALSO NOTE that those directories are usually write protected, even if
your account is in the Administrators group. To work around that,
start the command prompt by right-clicking on it and choosing "Run as
Administrator" before running 'nmake install'. The other solution
is, of course, to choose a different set of directories by using
--prefix and --openssldir when configuring.
Special notes for Universal Windows Platform builds, aka VC-*-UWP
- UWP targets only support building the static and dynamic libraries.
- You should define the platform type to "uwp" and the target arch via
"vcvarsall.bat" before you compile. For example, if you want to build
"arm64" builds, you should run "vcvarsall.bat x86_arm64 uwp".
Native OpenSSL built using MinGW
MinGW offers an alternative way to build native OpenSSL, by cross compilation.
* Usually the build is done on Windows in a GNU-like environment called MSYS2.
MSYS2 provides GNU tools, a Unix-like command prompt,
and a UNIX compatibility layer for applications.
However, in this context it is only used for building OpenSSL.
The resulting OpenSSL does not rely on MSYS2 to run and is fully native.
Requirement details
- MSYS2 shell, from
- Perl, at least version 5.10.0, which usually comes pre-installed with MSYS2
- make, installed using "pacman -S make" into the MSYS2 environment
- MinGW[64] compiler: mingw-w64-i686-gcc and/or mingw-w64-x86_64-gcc.
These compilers must be on your MSYS2 $PATH.
A common error is to not have these on your $PATH.
The MSYS2 version of gcc will not work correctly here.
In the MSYS2 shell do the configuration depending on the target architecture:
./Configure mingw ...
./Configure mingw64 ...
./Configure ...
for the default architecture.
Apart from that, follow the Unix / Linux instructions in
* It is also possible to build mingw[64] on Linux or Cygwin.
In this case configure with the corresponding --cross-compile-prefix= option.
For example
./Configure mingw --cross-compile-prefix=i686-w64-mingw32- ...
./Configure mingw64 --cross-compile-prefix=x86_64-w64-mingw32- ...
This requires that you've installed the necessary add-on packages for
mingw[64] cross compilation.
Linking your application
This section applies to all "native" builds.
If you link with static OpenSSL libraries then you're expected to
additionally link your application with WS2_32.LIB, GDI32.LIB,
ADVAPI32.LIB, CRYPT32.LIB and USER32.LIB. Those developing
non-interactive service applications might feel concerned about
linking with GDI32.LIB and USER32.LIB, as they are justly associated
with interactive desktop, which is not available to service
processes. The toolkit is designed to detect in which context it's
currently executed, GUI, console app or service, and act accordingly,
namely whether or not to actually make GUI calls. Additionally those
who wish to /DELAYLOAD:GDI32.DLL and /DELAYLOAD:USER32.DLL and
actually keep them off service process should consider implementing
and exporting from .exe image in question own _OPENSSL_isservice not
relying on USER32.DLL. E.g., on Windows Vista and later you could:
__declspec(dllexport) __cdecl BOOL _OPENSSL_isservice(void)
{ DWORD sess;
if (ProcessIdToSessionId(GetCurrentProcessId(),&sess))
return sess==0;
return FALSE;
If you link with OpenSSL .DLLs, then you're expected to include into
your application code a small "shim" snippet, which provides
the glue between the OpenSSL BIO layer and your compiler run-time.
See also the OPENSSL_Applink manual page.
Hosted OpenSSL built using Cygwin
Cygwin implements a POSIX/Unix runtime system (cygwin1.dll) on top of the
Windows subsystem and provides a Bash shell and GNU tools environment.
Consequently, a build of OpenSSL with Cygwin is virtually identical to the
Unix procedure.
To build OpenSSL using Cygwin, you need to:
* Install Cygwin, see
* Install Cygwin Perl, at least version 5.10.0
and ensure it is in the $PATH
* Run the Cygwin Bash shell
Apart from that, follow the Unix / Linux instructions in
NOTE: "make test" and normal file operations may fail in directories
mounted as text (i.e. mount -t c:\somewhere /home) due to Cygwin
stripping of carriage returns. To avoid this ensure that a binary
mount is used, e.g. mount -b c:\somewhere /home.