synology-thumbgen/ONEDRIVE_THUMBNAIL_FIX_README.md

OneDrive Thumbnail Override Fix

🎯 Problem Description

OneDrive's on-demand sync overrides locally-generated thumbnails with generic file icons when cloud services don't support specific file types (like .blend, .psd, etc.). This prevents you from seeing your custom thumbnails for unsupported formats.

🔍 Root Cause

1. OneDrive Files On-Demand uses cloud thumbnail providers that take precedence over local thumbnails
2. When OneDrive doesn't support a file type, it shows a generic file icon
3. This overrides your custom locally-generated thumbnails, even for files you've created beautiful previews for

✅ Solution Overview

This fix disables OneDrive's cloud thumbnail providers and restores priority to your local thumbnails while keeping OneDrive sync functionality intact.

🛠️ How to Use

Method 1: Automated PowerShell Script (Recommended)

1. Run the batch file:

   autoThumbs.bat
   

2. Select option 4: "Fix OneDrive thumbnail override"

3. Follow prompts - the script will run as administrator and fix the issue

Method 2: Manual Registry Fix

1. Run as Administrator:

   regedit
   

2. Import the registry file:

   disable_onedrive_thumbnails.reg
   

3. Restart Windows Explorer

Method 3: PowerShell Direct

Run PowerShell as Administrator and execute:

.\fix_thumbnail_override.ps1

📋 What Gets Changed

✅ Registry Modifications

1. OneDrive Policies:

   • HKCU\SOFTWARE\Policies\Microsoft\OneDrive → DisableCloudThumbnails = 1
   • HKLM\SOFTWARE\Policies\Microsoft\OneDrive → DisableCloudThumbnails = 1

2. Cloud Thumbnail Provider Removal:

   • Removes: HKLM\...\ThumbnailProviders\{E357FCCD-A995-4576-B01F-234630154E96}

3. Local Thumbnail Preferences:

   • HKCU\...\Explorer\Advanced → UseLocalThumbnailProvider = 1
   • HKCU\...\Explorer\Advanced → IconsOnly = 0

4. OneDrive Shell Overlays Disabled:

   • Removes OneDrive1-7 shell icon overlays that can interfere

5. Thumbnail Cache Protection:

   • Prevents Windows from auto-deleting thumbnail cache
   • HKLM\...\VolumeCaches\Thumbnail Cache → Autorun = 0

🔄 Process Changes

1. Explorer Process Restart - Clears cached thumbnail providers
2. Thumbnail Cache Regeneration - Forces fresh thumbnail creation
3. Local Provider Priority - Your custom thumbnails now take precedence

⚠️ Important Notes

✅ What Still Works

• ✅ OneDrive sync functionality (unchanged)
• ✅ File access and collaboration
• ✅ Cloud storage features
• ✅ Local thumbnail generation

❌ What Changes

• ❌ OneDrive won't override your custom thumbnails anymore
• ❌ Cloud-based thumbnail generation is disabled
• ❌ Some OneDrive visual overlays may be reduced

🔧 Troubleshooting

If thumbnails still don't appear:

1. Clear thumbnail cache manually:

   del /f /s /q "%LocalAppData%\Microsoft\Windows\Explorer\thumbcache_*.db"
   

2. Restart Windows Explorer:

   taskkill /f /im explorer.exe && start explorer.exe
   

3. Regenerate thumbnails:

   python psthumbgen.py --directory "Your\Directory\Path"
   

If you want to revert changes:

Use the restore registry file:

restore_onedrive_thumbnails.reg

🎉 Expected Results

After applying this fix:

1. Your custom thumbnails (like for .blend files) will display properly
2. OneDrive sync continues working normally
3. File access remains unchanged
4. Local thumbnail generation takes priority over cloud providers

📝 Technical Details

Cloud Thumbnail Provider GUID

The key provider that overrides local thumbnails:

• {E357FCCD-A995-4576-B01F-234630154E96} - Windows Cloud Files Thumbnail Provider

OneDrive Shell Overlays

These overlays can interfere with thumbnail display:

• OneDrive1 through OneDrive7 in ShellIconOverlayIdentifiers

Registry Locations

# User-level policies
HKCU\SOFTWARE\Policies\Microsoft\OneDrive

# Machine-level policies  
HKLM\SOFTWARE\Policies\Microsoft\OneDrive

# Thumbnail providers
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ThumbnailProviders

# Explorer settings
HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced

🔄 Maintenance

• Reboot required for full effect
• May need to reapply after major Windows updates
• Compatible with Windows 10/11 and current OneDrive versions

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🎨 Now you can enjoy your beautiful custom thumbnails without OneDrive interference!