Windows 11 reporting an error with pdfpreview.dll

[glomn]

SumatraPDF version

• Version 3.6.1 x64

Describe the bug
Windows 11's event viewer is reporting an error with pdfpreview.dll
Windows version is 25H2.

To Reproduce
Steps to reproduce the behavior:

1. Boot up and log in
2. Navigate to Event Viewer
3. Read the event details

Expected behavior
I haven't noticed previews not working but I'm not sure if this is just a harmless error or something that should be looked into. I've also recently installed outlook. I saw there's been some issues posted about that but I don't know if this could have something to do with it. Granted, I haven't tried opening any pdfs in outlook just yet.

File that reproduces the problem
There is no specific file

Screenshots*
If applicable, add screenshots to help explain your problem.

Additional context

[kjk]

Thanks for the report. There isn't quite enough here to pin it down yet — the screenshot tells us something faulted in pdfpreview.dll, but not where.

pdfpreview.dll is SumatraPDF's PDF preview handler. Windows doesn't load it into SumatraPDF itself — it loads it into a separate host process called prevhost.exe, which is the same host used by Explorer's preview pane and Outlook's reading pane. So your hunch about Outlook is plausible: previewing a PDF attachment there would exercise this DLL.

Could you help with one or both of the following?

1) The full Event Viewer text (not a screenshot)

Open Event Viewer → Windows Logs → Application, find the matching "Application Error" (Event ID 1000) entry (and, just below/above it, the "Windows Error Reporting" (Event ID 1001) entry), and copy the full text. The fields that matter:

• Faulting application name (e.g. prevhost.exe, dllhost.exe, or OUTLOOK.EXE)
• Faulting module name and version (should be pdfpreview.dll)
• Exception code
• Fault offset

The module version + fault offset is often enough for me to locate the crash in the code.

2) A crash dump (most useful)

You can have Windows capture a full dump automatically:

1. Open Registry Editor (regedit).
2. Go to (creating the keys if they don't exist):
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Windows Error Reporting\LocalDumps\prevhost.exe
3. Inside the prevhost.exe key, create these values:
   • DumpType — DWORD = 2
   • DumpFolder — Expandable String (REG_EXPAND_SZ) = e.g. C:\Dumps
4. Reproduce the error (e.g. select/preview a PDF in Explorer, or open a PDF attachment in Outlook).
5. A .dmp file should appear in that folder — please attach it here (or share a download link). You can delete the registry key afterwards.

If the Event Viewer entry shows a faulting application other than prevhost.exe (for example dllhost.exe or OUTLOOK.EXE), use that exact .exe name for the LocalDumps subkey in step 2 instead.

3) One quick question

Do PDF previews actually fail or look wrong, or do they work fine and this is only an Event Viewer entry? That helps me judge whether it's a real problem or a harmless log (e.g. a hiccup during host shutdown).

Thanks!

[kjk]

To help track this down, I've added opt-in logging to the PDF preview handler. If you can capture a log, it'll show what the handler was doing when the error fired.

Note: this is only in the latest pre-release build (not in 3.6.1). You can get it here: https://www.sumatrapdfreader.org/prerelease — install it, then:

1. Open SumatraPDF and press Ctrl+K to open the command palette.
2. Type "Toggle PDF Preview Logging" and run it. A notification will appear confirming logging is enabled and showing the folder where logs are written (something like C:\Users\<you>\AppData\Local\SumatraPDF-data\<id>).
   • The command only shows up for an installed SumatraPDF (not the portable .exe).
3. Reproduce the error — e.g. select/preview a PDF in Explorer's preview pane, or open a PDF attachment in Outlook's reading pane. (Each preview session writes its own log file.)
4. Open that folder and grab the newest pdfpreview.log.*.txt file, and attach it here.
5. When you're done, run "Toggle PDF Preview Logging" again to turn it back off.

If you'd rather not switch to a pre-release, the WER LocalDumps route from my previous comment (capturing a .dmp) works on your current 3.6.1 too — either one helps.

Thanks!