Windows caches every thumbnail it generates so folders open quickly on the second visit. The trade-off is that the cache also preserves mistakes: blank previews generated before a thumbnail handler such as SageThumbs was installed, corrupted entries after a crash, and stale images for files that have since changed. Clearing and rebuilding the cache is the standard first repair for wrong, missing or outdated thumbnails, and it is safe: you lose no image files, only temporary preview data that Explorer recreates on demand. SageThumbs itself (version 2.0.0.23, GPL v2 or later) also keeps its own cache file, sagethumbs.db3, which is covered in a separate guide. This article deals with the Windows cache, the one that affects every thumbnail handler on the system.
When a cache rebuild is the right fix
- Thumbnails are missing for formats that worked before, or generic icons replaced real previews.
- A folder shows previews for old versions of images you have edited or replaced.
- You installed SageThumbs and supported formats still show generic icons in icon views.
- Explorer shows a mix of correct and broken previews in the same folder with no pattern.
- A folder became sluggish after an Explorer crash while it was generating previews.
If instead no thumbnails appear anywhere at all, check the Explorer-wide settings first: an icon view must be selected and the Always show icons, never thumbnails option must be off. A cache rebuild cannot fix a setting that tells Explorer never to request thumbnails in the first place. Order matters in troubleshooting, and settings first, cache second, reinstall last will save you from repeating work.
Method 1: Disk Cleanup (the simple, recommended route)
- Open the Start menu, type Disk Cleanup, and open the app.
- Select your system drive, usually C:, and let the scan finish.
- In the list, tick Thumbnails. You do not need to tick anything else for this job.
- Click OK and confirm deletion. Windows removes the cached thumbnail databases.
- Restart Explorer from Task Manager or restart the PC, then open an image folder in Large icons view and let previews regenerate.
Disk Cleanup is the route most users should take because it targets exactly the right files with no manual folder hunting. Regeneration is not instant: the first opening of a large photo or design folder will be slower than usual while Explorer requests fresh previews from SageThumbs and other handlers and rebuilds the cache. Scroll through important folders once after the cleanup so their previews exist before you actually need them under time pressure.
Method 2: Delete the cache files manually
For users comfortable with hidden folders, the cache lives as a set of thumbcache database files under the Explorer folder inside your local AppData. Close Explorer windows first, then delete the thumbcache .db files in that folder; Windows recreates them automatically. Files that refuse to delete are in use, which usually means an Explorer process, preview pane or related service still holds them: restarting the PC and deleting before opening image folders resolves that. Do not delete anything outside the thumbnail cache files while you are there. If the manual route feels risky, stop and use Disk Cleanup instead; both routes achieve the same result and there is no prize for the harder one.
After the rebuild: set expectations and verify
Verify with a folder whose contents you know well. PSD files are a good test because they depend on SageThumbs rather than on Windows alone: after a successful rebuild with SageThumbs installed, PSD previews should appear in Large icons view. JPG and PNG previews should return quickly, while very large files and folders with thousands of images take longer. If one specific file still refuses to preview after a full rebuild while its neighbours succeed, the problem is the file itself or a format boundary, not the cache. Remember that SageThumbs covers 162 formats via the GFL Library and does not cover formats outside that list such as WebP, SVG, HEIC, AVIF, INDD or CR3, and that AI, EPS and PDF previews additionally need AFPL GhostScript 8.54.
Frequently asked questions
Will clearing the thumbnail cache delete any of my images?
No. The cache contains only temporary preview copies managed by Windows. Your original image files are never stored in the thumbnail cache and are not touched by either cleanup method in this guide.
How often should I rebuild the thumbnail cache?
Only when symptoms appear. There is no maintenance schedule for the cache; rebuilding on a healthy system just makes folders slower while previews regenerate. Treat it as a repair step, not a routine.
Thumbnails are still missing after a rebuild. What next?
Recheck the icon view and the icons-only setting, confirm SageThumbs previews work in a test folder, check its maximum file size option, and then follow the full thumbnails-not-showing checklist linked below.
Related guides
Keep exploring with these guides from this site:
- SageThumbs Thumbnails Not Showing? 8 Fixes
- What Is sagethumbs.db3?
- How to Enable PSD Thumbnails in Windows Explorer
Practical notes before you move on
Keep a short note of what you changed and what you observed while working through this guide. Explorer thumbnail problems often return in a slightly different form months later, after a Windows update, a new drive or a change in the kind of files you handle, and a dated note turns the second diagnosis into a five-minute repeat of a known fix instead of a fresh investigation. Note the Windows version, the SageThumbs version (2.0.0.23), the folder and file types involved, and which step actually restored the previews. If a step did nothing, note that too: ruling causes out is real progress, and it keeps the next troubleshooting session focused on what remains.