How to get GUIDs of COM classes from the interface names used in the Windows API documentation?

Question

What is the correct way to find the GUID (for instance {1C158861-B533-4B30-B1CF-E853E51C59B8}) for a given COM class named in the Windows SDK documentation (for instance IChannelAudioVolume)?

I'm working on a Python script that sets Windows audio mixer settings for individual applications that are playing audio (audio sessions). I want to set the channel volumes, to pan the audio, which is built-in Windows functionality exposed by the IChannelAudioVolume API.

I see that pycaw uses many COM-based Windows APIs through comtypes, starting with declarations that provide the GUID, parent interface, and method details to comtypes:

from ctypes import HRESULT, POINTER, c_uint32, c_float
from comtypes import IUnknown, GUID, COMMETHOD

class ISimpleAudioVolume(IUnknown):
    _iid_ = GUID('{87CE5498-68D6-44E5-9215-6DA47EF883D8}')
    _methods_ = (
        # HRESULT SetMasterVolume(
        # [in] float fLevel,
        # [in] LPCGUID EventContext);
        COMMETHOD([], HRESULT, 'SetMasterVolume',
                  (['in'], c_float, 'fLevel'),
                  (['in'], POINTER(GUID), 'EventContext')), # ...

Where does someone writing this kind of code find out these GUIDs (e.g. '{87CE5498-68D6-44E5-9215-6DA47EF883D8}') that correspond to particular interface names? They are not in the main documentation for the individual interfaces. Are they documented officially somewhere? Alternately, is there something that I can run to look them up from the interface name (e.g. ISimpleAudioVolume) in Windows?

In the meantime, I'm just Googling the name of the interface I'm looking for, along with GUID values of thematically-similar interfaces without the {}, and hoping to come across other code samples that have them. This works well enough for my immediate purposes, but is hit or miss, and it's unclear whether the GUIDs I find this way are intended as public APIs.

Answer 1

This online tool MagnumDb as "Magic Number Database" (disclaimer: I wrote it) is a totally free seach engine that contains 99% of Windows SDK constants with more than 70K guids (IID, CLSID, etc.).

You can query it by name or by value, using wildcards, etc., for example: http://www.magnumdb.com/search?q=IChannelAudioVolume

will get you this (name, type, value, SDK header file location):

IID_IChannelAudioVolume Guid    1c158861-b533-4b30-b1cf-e853e51c59b8    %ProgramFiles(x86)%\Windows Kits\10\Include\10.0.17134.0\um\Audioclient.h(1942,0)

Answer 2

The Windows SDK contains interface definition (IDL) files alongside the C/C++ header files in the Include directories, and these contain the GUIDs.

The MSDN API documentation for an interface, for instance IChannelAudioVolume, provides the C/C++ header file name in the Requirements box near the bottom of the page. For IChannelAudioVolume, it is Audioclient.h. Search the SDK directory for that filename, to find the subdirectory where that header file is found, in this case

C:\Program Files (x86)\Windows Kits\8.0\Include\um

There you will find an associated IDL file Audioclient.idl.

This has a section for each interface, where you can find the GUIDs, e.g.:

//-----------------------------------------------------------------------------
// Description: IChannelAudioVolume interface
//
[
    object,
    uuid(1C158861-B533-4B30-B1CF-E853E51C59B8),
    // ...

Answer 3

I wrote a project which analyzes the Windows SDK and parses all header files to extract this information: https://github.com/Elmue/WindowsRT-GUID-Analyzer

It auto-generates INI, XML, HTML, C# and C++ files for getting an interface name from a given GUID.

You don't need to install Windows SDK. I uploaded the auto-generated files.

Here you see your interface in the auto-generate C# code:

Dictionary<String,String> mi_Interfaces = new Dictionary<String,String>();
....
mi_Interfaces["96236A83-9DBC-11DA-9E3F-0011114AE311"] = "ISimilarity";
mi_Interfaces["96236A7F-9DBC-11DA-9E3F-0011114AE311"] = "ISimilarityFileIdTable";
mi_Interfaces["96236A7A-9DBC-11DA-9E3F-0011114AE311"] = "ISimilarityReportProgress";
mi_Interfaces["96236A7B-9DBC-11DA-9E3F-0011114AE311"] = "ISimilarityTableDumpState";
mi_Interfaces["96236A7C-9DBC-11DA-9E3F-0011114AE311"] = "ISimilarityTraitsMappedView";
mi_Interfaces["96236A7D-9DBC-11DA-9E3F-0011114AE311"] = "ISimilarityTraitsMapping";
mi_Interfaces["96236A7E-9DBC-11DA-9E3F-0011114AE311"] = "ISimilarityTraitsTable";
 mi_Interfaces["87CE5498-68D6-44E5-9215-6DA47EF883D8"] = "ISimpleAudioVolume";
mi_Interfaces["5E341AB7-02D0-11D1-900C-00A0C9063796"] = "ISimpleCommandCreator";
mi_Interfaces["51973C3E-CB0C-11D0-B5C9-00A0244A0E7A"] = "ISimpleConnectionPoint";
mi_Interfaces["742B0E01-14E6-101B-914E-00AA00300CAB"] = "ISimpleFrameSite";
mi_Interfaces["9A189741-DED1-4535-B116-B6D287BF70D2"] = "ISimpleModemCompletion";
mi_Interfaces["892FB9B0-7C55-4A18-9316-FDF449569B64"] = "ISingleItemException";
mi_Interfaces["624B5CA7-FE40-4957-A019-20C4CF11920F"] = "IsItemContainerPatternAvailable_Property_GUID";
mi_Interfaces["B4563688-98EB-4646-B279-44DA14D45748"] = "ISketchInk";
....

The file containing 25600 interfaces can be downloaded here: All Windows 11 Interfaces - C# Windows GUID Database

There is also a *.XML, *.HTM, *.CS and *.H file.

You can simply modify the project to output the data in reverse order: Input=Interface Name --> Output=GUID and you can modify the CSharp template to generate Python code instead.