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Brian Gianforcaro edited this page Jul 21, 2021 · 8 revisions

Detours Frequently Asked Questions (FAQ)

This page contains a list of questions frequently asked about Detours. The questions are grouped by general topic and area of interest.


Is Detours compatible with Windows 10?

Yes. Detours is fully compatible with Windows 10 desktop and server applications. While Detours can be used in the development and testing of Window Store apps, new Windows Store apps for Windows 10 can not ship with Detours.

Why can't my Windows Store app for Windows 10 include Detours?

Windows Store apps may use only a subset of the Win32 API. Detours requires several Win32 APIs that are forbidden in for Windows App Certification. Forbidden APIs used by Detours include VirtualAlloc, VirtualProtect, and FlushInstructionCache.

Is Detours compatible with Windows 95, Windows 98, or Windows ME?

No. Detours is compatible only with the Windows NT family of operating systems: Windows NT, Windows XP, and Windows Server 2003, etc. Detours does not work on the Windows 9x family of operating systems because they have a primitive virtual memory system.

Compiling with Detours Code

How do I do thing X with Detours?

Look in the Detours Samples. The Detours Samples are quite extensive. It is likely that anything you want to accomplish with Detours is covered in one of the included samples.

Where can I find detours.lib and detours.h?

You need to build a version of detours.lib for your C/C++ compiler. The steps to build detours are:

  1. Initialize the Microsoft C++ toolset command line environment for the architecture you are targeting.

  2. Clone the Detours repository: git clone

  3. Build with nmake

    a. To build just the detours library, change to the detours/src directory and run the nmake command.

    b. To build detours and the samples, change to the detours directory and run the nmake command.

  4. A lib.<ARCH> directory should now exist, containing the Detours static library, where <ARCH> is the target architecture you are compiling for. The include directory will also be generated during the build, it contains the headers for the library.

    C:\detours> dir /b *.x64

    C:\detours> dir /b lib.X64

    C:\detours> dir /b include

Running with Detours

Why don't I see any calls to my detour of malloc?

Probably because the target program is not using the malloc function you detoured.

Standard library functions like malloc can be linked with a program either statically, from one of the libc*.lib libraries, or dynamically, from one of the msvcrt*.dll libraries. When statically linked, a program receives its own private version of the standard library functions. When dynamically linked, a program shares version of the standard library functions in a DLL. If you detour your private version of the function, or if the target program uses its own private version of the function, your detour won't be called by the target program.

Why is Detours packaged as a static library (detours.lib) and not as a dynamic link library (say detours.dll)?

Packaging Detours as a statical library minimizes the risk that you will accidentally detour a function required by the Detours package itself and reduces versioning problems. Note that Detours adds only about 16KB when statically linked with your code.

Do I still need to use detoured.dll?

No, the detoured.dll marker file was removed in Detours 3.0. Before Detours 3.0, this file was used as marker to guide Microsoft technical support personnel and tools, like Windows Error Reporting, by helping them quickly determine that a process has been altered by the Detours package. Advances in Windows OCA in Windows 7 removed the need for this marker as Windows 7 maintains a list of DLL that have been unloaded from a process. Microsoft can not guarantee nor support in any way, the modification of Microsoft binaries by third parties. Nor can Microsoft support, in any way, an application that contains Microsoft binaries modified by third parties. This includes in-memory modification using the Detours package.

How can I debug the startup of my detour DLL?

The Windbg can single step or break on exceptions in process startup. Windbg is available in the "Debugging Tools for Windows" download from on For example, you can use the command line:

windbg -o withdll.exe -d:mydll.dll myexe.exe

It is also possible to debug child process startup in Visual Studio by using the Microsoft Child Process Debugging Power Tool extension. Once installed you'll need to enable child process debugging using the extension, detailed instructions on how to achieve this can be found in the blog post announcing the extension.

Why does my code act differently under a debugger?

Debuggers insert breakpoints by replacing function code with break instructions. For example, on the X86 and X64 processors, the debugger will write a 0xCC (int 3) for a breakpoint. If the breakpoint is written before a detour is applied, the Detour library will see the 0xCC instead of the real instructions.

The best way to work around this issue is to ensure that no debugger breakpoints are set on target functions.


Can Detours be used in commercial applications?

Detours is licensed under the MIT license, which allows commercial use.

Bug Reports

How do I report a bug or an issue?

Please open an issue on the GitHub issue tracker system. In your issue, please be sure to include the version of Detours that are you are using. Before opening an issue, please make every effort to ensure that the problem is not an error in your own code or your usage of Detours. The most common sources of user error are covered in this FAQ.

You can also send detailed bug reports to Please include the text "DETOURS BUG REPORT" in the subject line. Within the body of your message, please include the first line from the README.TXT file which contains the full description of the version Detours you are using including the Build number.

The email address is for bug reports only, it is not a product support line.

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