Startup crash in qwindows.dll on Windows 11 24H2 with OBS 32.0.2 and 31.x portable; OBS 27 works

[quidscio]

Operating System Info

Windows 11

Other OS

No response

OBS Studio Version

32.0.2

OBS Studio Version (Other)

No response

OBS Studio Log URL

https://obsproject.com/logs/4fLE55JJ2vyrRbrY

OBS Studio Crash Log URL

https://obsproject.com/logs/FRMcO1nwJZl6mkiq

Expected Behavior

OBS 32.0.2 and 31.1.2 should start and display the main window, or the safe mode dialog if an unclean shutdown was detected.

Current Behavior

OBS 32.0.2 and 31.1.2 crash immediately when starting the portable build.

Example crash from OBS 32.0.2 (portable) after deleting .sentinel:

• Exception: Unhandled exception: c0000005

• Fault module: qwindows.dll

• Fault address, for example:

  Fault address: 7FFF148FB611 (c:\tools\obs-studio-32.0.2-windows-x64\bin\64bit\platforms\qwindows.dll)

• Call stack (top part of crashed thread):

  qwindows.dll!0x7fff148fb611
  qwindows.dll!0x7fff148fac9f
  qwindows.dll!0x7fff148c1e74
  qt6gui.dll!0x7ffeba4e09c1
  qt6widgets.dll!0x7ffebb7d248c
  qt6widgets.dll!0x7ffebb7d1c11
  qt6widgets.dll!0x7ffebb7f0232
  obs64.exe!OBSBasic::OBSInit+0xd64
  obs64.exe!OBSApp::OBSInit+0x3b6
  obs64.exe!run_program+0xb22
  obs64.exe!main+0x722
  obs64.exe!qtEntryPoint+0x30
  kernel32.dll
  ntdll.dll

Earlier crash logs (before I removed .sentinel) sometimes showed the stack going through obs64.exe!handleUncleanShutdown, but in all cases the fault module is qwindows.dll and the crash occurs while Qt is initializing the OBS window.

Steps to Reproduce

For OBS Studio 32.0.2:

1. On Windows 11 24H2 build 26100.7171, download the Windows 64 bit portable ZIP for OBS Studio 32.0.2.
2. Extract to C:\Tools\OBS-Studio-32.0.2-Windows-x64.
3. Optionally create portable_mode.txt in the root so OBS uses a local config.
4. In bin\64bit, run obs64.exe.
5. OBS crashes within about a second. No window appears. Sometimes a crash report file is written, sometimes not.

The same behavior occurs with OBS Studio 31.1.2 portable:

1. Download OBS Studio 31.1.2 Windows 64 bit portable ZIP.
2. Extract to C:\Tools\OBS-Studio-31.1.2-Windows-x64.
3. Run bin\64bit\obs64.exe.
4. OBS crashes immediately in the same way.

On the same system, OBS Studio 27.2.4 portable:

1. Extract 27.2.4 to C:\Tools\OBS-Studio-27.2.4-Full-x64.
2. Run bin\64bit\obs64.exe.
3. OBS starts and works normally as long as the renderer is left at the default (Direct3D 11). Switching to the OpenGL renderer makes the preview blank, so I switched back to D3D11.

Anything else we should know?

Also posted to Discord: https://discord.com/channels/348973006581923840/374636015396192257/1440031930148978708

And, things I have already tried

All of the following were done on this system:

• Used portable builds only (no installer, no shared plugins).

• Confirmed there are no third party OBS plugins in the portable folders.

• Deleted the .sentinel folder from OBS config:

  • %APPDATA%\obs-studio

  • portable config directory (with portable_mode.txt present)

• Updated NVIDIA GPU driver from an older August driver to 581.80 from NVIDIA as of 2025 11 16.

• Confirmed Intel iGPU driver version 32.0.101.7026 (Windows 11 DCH driver).

• Installed the latest Intel, Lenovo, Realtek and Windows Security updates offered by Windows Update.

• Turned off:

  • Hardware Accelerated GPU Scheduling

  • “Optimizations for windowed games”

• Forced OBS to use each GPU via Windows 11 Graphics settings:

  • “High performance” (NVIDIA RTX 4090 Laptop GPU)

  • “Power saving” (Intel Iris Xe)

• Disabled overlays and capture hooks:

  • NVIDIA overlay

  • Xbox Game Bar

  • Discord overlay

  • Other obvious overlay or capture tools

• Ran sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth:

  • First sfc pass found corrupt files and repaired them.

  • Second sfc pass reports no integrity violations.

  • DISM completed successfully.

• Tried starting OBS with Qt environment variables to force software or OpenGL paths. For example:

  set QT_PLUGIN_PATH=
  set QT_QPA_PLATFORM_PLUGIN_PATH=
  set QT_QPA_PLATFORM=windows
  set QT_OPENGL=software
  set QSG_RHI_BACKEND=opengl
  set QSG_RHI_PREFER_SOFTWARE_RENDERER=1
  
  obs64.exe --disable-high-dpi-scaling --verbose
  

  OBS 32.0.2 still crashes in qwindows.dll with the same kind of stack as shown above.

• For OBS 27.2.4 portable:

  • OBS starts and runs correctly with the default renderer (Direct3D 11).

  • Switching to the OpenGL renderer causes a blank preview, so I left it on D3D11.

This looks like a Qt 6 startup crash in qwindows.dll that affects OBS 32.0.2 and 31.1.2 on Windows 11 24H2 on this hardware, while OBS 27.2.4 is able to run on the same system using D3D11.

[quidscio]

At Discord suggestion this issue could be unique to my system, removed and disabled everything possible including:

• WinTV app, drivers, hardware
• XSplit virtual camera
• Clean boot via msconfig, disabled all non-Microsoft services

Re-running version 32 in portable mode free of all plugins, the app still crashes before GUI.
I have a Sysinternals ProcDump I can share privately if that helps.
While open to ideas for further elimination, system-specific characteristics have been reduced dramatically.

Latest ProcDump run and dump availability

For the most recent run I captured a full user mode dump of obs64.exe using Sysinternals ProcDump, still in the clean boot environment described above.

• Command line used from the portable folder:

  obs64.exe --disable-high-dpi-scaling --verbose
  

• ProcDump command:

  procdump64.exe -accepteula -e -ma -x C:\Temp\obs_dumps obs64.exe --disable-high-dpi-scaling --verbose
  

• Crash log for this run still shows the same access violation in qwindows.dll as earlier runs:

  Unhandled exception: c0000005
  Date/Time: 2025-11-17, 19:30:07
  Fault address: 7FFE3F59B611 (c:\tools\obs-studio-32.0.2-windows-x64\bin\64bit\platforms\qwindows.dll)
  libobs version: 32.0.2 (64-bit)
  Windows version: 10.0 build 26100 (release: 24H2; revision: 7171; 64-bit)
  CPU: 13th Gen Intel(R) Core(TM) i9-13900H
  
  qwindows.dll
  qwindows.dll
  qwindows.dll
  qt6gui.dll
  qt6widgets.dll
  qt6widgets.dll
  qt6widgets.dll
  obs64.exe!`anonymous namespace'::handleUncleanShutdown+0x3c5
  obs64.exe!run_program+0x65d
  obs64.exe!main+0x722
  obs64.exe!qtEntryPoint+0x30
  kernel32.dll
  ntdll.dll
  

• The corresponding OBS log for that run is very short and just reports a crash or unclean shutdown on startup.

ProcDump wrote a full user mode dump for obs64.exe to C:\Temp\obs_dumps, which I have zipped and saved. Since a full dump can contain process memory (paths with my username, in memory config, etc.), I would prefer not to attach it directly to this public issue.

If a dump would be useful to debug this qwindows.dll startup crash on Windows 11 24H2 with this hybrid GPU configuration, I am happy to share the zipped dump via a private link (OneDrive, Google Drive, or any upload location you prefer). Please let me know how you would like me to provide it and I will upload it right away.

Environment

• Windows 11 Pro 24H2, Version 10.0.26100.7171, 64 bit.
• Hybrid GPU laptop with:
  • Intel Iris Xe Graphics, driver 32.0.101.7026
  • NVIDIA GeForce RTX 4090 Laptop GPU, driver 581.80 (NVIDIA-SMI 581.80, CUDA 13.0)
• OBS Studio 32.0.2 Windows 64 bit portable ZIP in C:\Tools\OBS-Studio-32.0.2-Windows-x64.
• No third party OBS plugins in the portable tree.

Troubleshooting and isolation done so far

• Verified Windows system files:
  • Ran DISM /Online /Cleanup-Image /RestoreHealth.
  • Ran sfc /scannow twice. First pass repaired files, second pass reported no integrity violations.
• Updated software:
  • Installed latest Windows updates (including Lenovo, Intel, Realtek items) from Windows Update.
  • Updated NVIDIA GPU driver to 581.80.
  • Confirmed Intel GPU driver version 32.0.101.7026.
• OBS versions tested:
  • 27.2.4 portable: starts and runs correctly with the default D3D11 renderer. If I switch 27.2.4 to the OpenGL renderer the preview goes blank, so I leave it on D3D11.
  • 31.1.2 portable: crashes at startup with the same qwindows.dll access violation as 32.0.2.
  • 32.0.2 portable: crashes at startup with qwindows.dll before any UI appears.
• Config reset:
  • Deleted .sentinel from %APPDATA%\obs-studio.
  • Created portable_mode.txt and deleted .sentinel from the portable config directory.
  • After that, 32.0.2 still crashes, but the stack sometimes goes through OBSBasic::OBSInit instead of the unclean shutdown handler. In all cases the fault is still in qwindows.dll while Qt is initializing.
• Graphics settings:
  • Turned off Hardware Accelerated GPU Scheduling and "Optimizations for windowed games".
  • Used Windows Graphics settings to prefer both GPUs for obs64.exe in separate tests:
  • Intel iGPU as "Power saving".
  • NVIDIA dGPU as "High performance".
  • Tried Qt environment variables to force different backends for 32.0.2 portable, for example:
  • QT_QPA_PLATFORM=windows
  • QT_OPENGL=software
  • QSG_RHI_BACKEND=opengl
  • QSG_RHI_PREFER_SOFTWARE_RENDERER=1
  • These did not change the crash, which still occurs in qwindows.dll very early in startup.
• TV tuner and virtual camera:
  • Uninstalled WinTV v10 and unplugged the Hauppauge WinTV-dualHD USB tuner. Device Manager now shows the Hauppauge entry only as an inactive device that cannot be disabled further. OBS 32 still crashes the same way without the tuner present.
  • Disabled XSplit VCam under "Imaging devices" in Device Manager. Confirmed it is disabled. OBS 32 still crashes in qwindows.dll.
• Clean boot:
  • In msconfig I checked "Hide all Microsoft services" and clicked "Disable all" to disable every non Microsoft service.
  • Rebooted and confirmed only Microsoft services plus one Intel graphics related service are running.
  • In this clean boot state, with WinTV removed and XSplit VCam disabled, OBS 32.0.2 and 31.1.2 portable still crash immediately in qwindows.dll on startup.
• All of the above tests were done with portable builds, no third party OBS plugins, and no additional overlays that I am aware of.

[Fenrirthviti]

Thanks for the detailed information. The dump would definitely be helpful, if you want to send it to Fenrir (discord username Len) on the OBS Discord, I can get it to the right folks to take a look.

[quidscio]

Completed. Thanks much!

[wanhongqing123]

the crash location is:

void SetWin32DropStyle(QWidget *window)
{
HWND hwnd = (HWND)window->winId();
LONG_PTR ex_style = GetWindowLongPtr(hwnd, GWL_EXSTYLE);
ex_style |= WS_EX_ACCEPTFILES;
SetWindowLongPtr(hwnd, GWL_EXSTYLE, ex_style);
}

when call ‘window->winId()’ crashed in qt. maybe this windows is not show.

[wanhongqing123]

I discovered that this theme hasn't been created in Qt6 yet. For example: mov this, cs:?m_instance@QWindowsTheme@@0PEAV1@EA ; QWindowsTheme * QWindowsTheme::m_instance

[wanhongqing123]

Could you tell me where I can download the Qt6 source code?

[wanhongqing123]

#12834 maybe is helpful

[quidscio]

Thank you for the dev build to try.

Tested in portable mode the 32.0.2 dev build on my system with GPU features turned off and captured a full user-mode dump via ProcDump.

Crash still occurs before any OBS window appears.

I do not have authoritative info on QT6 source (assuming this was a me question). Best is https://github.com/qt/qtbase.

2025-11-18 10-15-24.txt

Crash 2025-11-18 10-15-26.txt

Environment

• Windows 11 Pro 24H2 (10.0.26100.7171), 64-bit
• CPU: 13th Gen Intel(R) Core(TM) i9-13900H
• Hybrid GPU laptop:
  • Intel(R) Iris(R) Xe Graphics
  • NVIDIA GeForce RTX 4090 Laptop GPU (driver 581.80)
• Global graphics settings:
  • Hardware Accelerated GPU Scheduling: Disabled
  • “Optimizations for windowed games”: Disabled

Build and command

• Build: OBS 32.0.2-3513f1e27 (64-bit, windows) portable ZIP in C:\tools\obs-studio-32.0.2-3513f1e27-windows-x64

• No third-party OBS plugins in the portable tree

• Launched under ProcDump with:

  procdump64.exe -accepteula -e -ma -x C:\Temp\obs_dumps obs64.exe --disable-high-dpi-scaling --verbose
  

Result

• OBS main window never appears.

• The OBS log for this run is essentially just:

  10:15:24.020: Crash or unclean shutdown detected

• Crash report shows an access violation in qwindows.dll very early in startup:

  Unhandled exception: c0000005
  Date/Time: 2025-11-18, 10:15:26
  Fault address: 7FFA9940B611 (c:\tools\obs-studio-32.0.2-3513f1e27-windows-x64\bin\64bit\platforms\qwindows.dll)
  libobs version: 32.0.2 (64-bit)
  Windows version: 10.0 build 26100 (release: 24H2; revision: 7171; 64-bit)
  CPU: 13th Gen Intel(R) Core(TM) i9-13900H

  qwindows.dll
  qwindows.dll
  qwindows.dll
  qt6gui.dll
  qt6widgets.dll
  qt6widgets.dll
  qt6widgets.dll
  obs64.exe!`anonymous namespace'::handleUncleanShutdown+0x3ee
  obs64.exe!OBSApp::checkForUncleanShutdown+0x2e
  obs64.exe!run_program+0x63e
  obs64.exe!main+0x603
  obs64.exe!qtEntryPoint+0x30
  kernel32.dll
  ntdll.dll

Crash file Crash 2025-11-18 10-15-26.txt and the short OBS log are attached.

Dump availability

ProcDump produced a full user-mode dump for obs64.exe. I am able to share this via private link. If helpful, let me know how I can do so.

[PatTheMav]

Both crashes have the same root cause, the differences in call stacks might very well be related to different compiler optimisation levels. They both crash because the creation of a QDialog fails (due to QWindowsTheme::instance() in QWindowsWindowData WindowCreationData::create returning a nullptr).

As this is a crash deep within Qt, we need the library to log more information, so could you please run OBS again in a command prompt like this (assuming cmd.exe) after changing to OBS Studio's binary directory:

set QT_DEBUG_PLUGINS=1
set QT_WIN_DEBUG_CONSOLE=attach

obs64.exe --verbose --portable

This should make Qt log general output but also debug information about plugin loading to the console window. Please copy that output into a text file and attach it as a comment to this issue.

[quidscio]

QT log file attached. Thanks for idea.

QT_log.txt

[PatTheMav]

QT log file attached. Thanks for idea.

QT_log.txt

Thanks, so it looks like all required platform plugins (that should take care of setting up the windows platform environment) are found and loaded. I also read that the issue also occurs when no sentinel directory is present, so it should not exclusively be triggered by the crash handling dialog, but might then potentially be triggered by another dialog (of which OBS might show quite a few).

Unfortunately the second dump was used with a OBS version created by CI, so the PDBs available to resolve symbols in the dump don't match it, so we can't see which other dialog triggered it, but I don't expect that to make much difference here.

[quidscio]

Quick follow up, this time with the correct debug build.
I incorrectly assumed the debug build was a one-time thing.

I have now rerun everything with the debug build provided earlier.
There are two runs.

1. Debug build with only your requested Qt logging

For the first run I used only the env vars you asked for:

set QT_DEBUG_PLUGINS=1
set QT_WIN_DEBUG_CONSOLE=attach

obs64.exe --disable-high-dpi-scaling --verbose --portable

Result:

• Debug build still crashes on startup before the main OBS window appears.

• The Qt plugin log shows qwindows.dll loaded from the debug build’s platforms folder, styles and image plugins load, then the app exits with an access violation in qwindows.dll in the same early startup path as before.

• I attached the updated crash report (Crash 2025-11-19 13-26-30.txt) and Qt console log (issue_debug-build.txt) for this run.
  Crash 2025-11-19 13-26-30.txt
  issue_debug-build.txt

2. Debug build with additional Qt logging and ProcDump full dump

For the second run I added a more explicit Qt environment and captured a full user-mode dump via ProcDump:

cd /d "C:\Tools\obs-studio-debug\bin\64bit"

rem Clear any global Qt overrides
set QT_PLUGIN_PATH=
set QT_QPA_PLATFORM_PLUGIN_PATH=
set QT_QPA_PLATFORM=windows

rem Prefer software / OpenGL instead of D3D11
set QT_OPENGL=software
set QSG_RHI_BACKEND=opengl
set QSG_RHI_PREFER_SOFTWARE_RENDERER=1

rem Extra logging
set QSG_INFO=1
set QT_DEBUG_PLUGINS=1
set QT_WIN_DEBUG_CONSOLE=attach
set QT_LOGGING_RULES=qt.qpa.*=true

"C:\Tools\Procdump\procdump64.exe" -accepteula -e -ma -x C:\Temp\obs_dumps ^
    obs64.exe --disable-high-dpi-scaling --verbose --portable

Result:

• Debug build again crashes before the main window, with an unhandled exception in qwindows.dll.

• Qt logs show the same general flow as the first debug run (platform plugin and styles load correctly, QPA activity begins, then the app dies during early window handling).

• ProcDump captured a full user-mode dump of obs64.exe for this debug build run in C:\Temp\obs_dumps. I have zipped this dump and can share it.

• Files: Crash 2025-11-19 13-34-59.txt and issue_debug-build_with-new-dump.txt
  Crash 2025-11-19 13-34-59.txt
  issue_debug-build_with-new-dump.txt

I can share the new dump privately via Google Drive link. LMK how if you like.

Also, I've done some other testing to further rule out unique apps, fonts, etc. I'll document via separate comment.

[quidscio]

Additional tests since last update

I ran a few more isolation tests focused on Qt windowing, fonts, and Windows security settings.
Short story, adopting single monitor, checking Windows Exploit protection, eliminating user fonts, running in a new & clean user did not prevent the crash.

1. Qt logging and single monitor

   • Ran the prod portable build with
     QT_DEBUG_PLUGINS=1
QT_WIN_DEBUG_CONSOLE=attach
QT_LOGGING_RULES=qt.qpa.*=true
   • Tested with only the internal laptop display active.
   • Qt logs show the expected platform plugin qwindows.dll and style plugins loading correctly, then normal qt.qpa activity, followed by
     QWindowsContext::windowsProc: No Qt Window found for event 0x1c (WM_ACTIVATEAPP)
     right before the crash. No plugin load failures or obvious font errors.

2. Windows Exploit protection and window utilities

   • Checked Exploit protection system settings: all at Windows defaults (CFG On, DEP On, Mandatory ASLR Off, Bottom up ASLR On, High entropy ASLR On, SEHOP On, Validate heap integrity On).
   • Exported Program settings to XML. There are overrides only for Office, IE, and some Windows components, but no entry for obs64.exe or Qt DLLs.
   • Exited PowerToys and other window related utilities and re-tested. Crash pattern did not change.

3. Font cache reset

   • Stopped the Windows Font Cache services where possible.
   • Deleted FNTCACHE.DAT in C:\Windows\System32.
   • Deleted ~FontCache-*.dat cache files under
     C:\Windows\ServiceProfiles\LocalService\AppData\Local\FontCache
     (left the locked FontCache-System.dat files that dwm.exe holds open).
   • Rebooted and reran the prod portable build with the same Qt logging env vars.
   • Result: crash still occurs in qwindows.dll at startup. Qt log now shows a complete pass over the DirectWrite font database and still ends with the same QWindowsContext::windowsProc message and access violation.

4. New Windows user profile

   • Created a brand new local user account with default settings.
   • Logged into that account, copied the prod portable OBS folder, and ran with the same command line and Qt env vars.
   • C:\Users\<newuser>\AppData\Local\Microsoft\Windows\Fonts is empty in this account.
   • OBS still crashes with the same unhandled access violation in qwindows.dll during very early startup.

5. User fonts

   • On my main account, C:\Users\rmhin\AppData\Local\Microsoft\Windows\Fonts is also empty, so all fonts seen in the Qt logs are system wide fonts from C:\Windows\Fonts.

Summary

• Crash reproduces with font cache cleared and rebuilt.
• Crash reproduces under a completely new Windows user profile with default settings.
• Exploit protection has no per program mitigations for obs64.exe.
• PowerToys and other window tools do not appear to affect the behavior.
• In all cases, the prod build still fails with the same access violation inside qwindows.dll while Qt processes early Windows messages, before the main OBS window appears.

[PatTheMav]

QT log file attached. Thanks for idea.

QT_log.txt

Can you give this one further try, but this time with these environment variables:

set QT_LOGGING_RULES='*.debug=false;qt.qpa.window=true;qt.qpa.theme=true;qt.qpa.plugin=true'
set QT_WIN_DEBUG_CONSOLE=attach

obs64.exe --verbose --portable