Photos, videos, and PDFs in a folder should show small preview images, but instead every one turns into the same file icon, and finding anything means opening files one by one. Thumbnails not showing is a common and very fixable problem, and it is a different matter from file extensions being hidden. This guide covers why previews turn into icons, how to switch them back on, rebuild the cache, and fix them by file type.

What Is Thumbnails Not Showing

Thumbnails not showing means the spot where a small preview image should be has turned into a uniform icon, leaving you with only the file name to judge by.

  • Every file becomes an icon, usually because Always show icons, never thumbnails is ticked or the thumbnail cache is damaged.
  • Only one type will not show, usually a missing codec or preview handler for that format.
  • A work or school machine suddenly stops showing them, possibly a group policy disabling thumbnails.

Tell a total failure from a single type first and the direction is clear. It does not touch the files themselves; only the preview is broken, and a double click still opens everything, so there is no sign the data is damaged.

What It Does

A thumbnail looks decorative, but fixing it speeds up finding files in a real way.

  • Recognise contents fast. Scanning pictures, videos, and PDFs beats opening them one at a time.
  • Catch a setting turned off. Optimisation tools often disable thumbnails to save resources, and switching it back is enough.
  • Locate a damaged cache. Clearing and rebuilding rescues previews that have gone blank.
  • Add missing codecs. Videos or RAW files with no preview often just need a codec or a player installed.

With many images and videos, a glance at a preview finds the right file far faster than reading names. It is a small fix that pays off every time you open a busy folder.

When to Use

  • Pictures and videos in a folder all show the same icon with no hint of the content.
  • Previews vanished after a system reinstall or a cleanup tool ran.
  • Only videos or only PDFs have no preview while other types are fine.
  • A company machine is tightly managed and you suspect policy is blocking them.
  • Files on a USB stick or a network drive take forever to show a preview.
  • The cache looks damaged and you want to rebuild it once.
  • Previews disappeared in a group after an optimiser or cleaner ran.

Before You Start

Confirm two things first to avoid wasted effort.

The thumbnail mechanism is the same on Windows 10 and Windows 11, and the cache lives in the same place. Nothing here changes the files themselves, so you can work through it in order.

ItemWindows 10Windows 11
Folder OptionsExplorer > View > OptionsSame
Cache directorythumbcache_*.dbSame

Step-by-Step

  1. Make sure Always show icons, never thumbnails is off. In Folder Options open the View tab, clear that box, click Apply to Folders, and let Windows rebuild previews over time. This single setting is the cause more often than anything else.
  2. Rebuild the thumbnail cache. Press Win + R, type cleanmgr, select the C drive, tick Thumbnails, and confirm; Windows regenerates them the next time you browse.
  3. Clear the cache by hand. Close every Explorer window, go to C:\Users\your-name\AppData\Local\Microsoft\Windows\Explorer, delete the thumbcache_*.db files, and restart. Use the deeper clean only when Disk Cleanup did not help.
  4. Add a codec for the type that will not show. Install a player for video, get the image extensions from the Store for RAW or WebP, and for PDFs install a preview handler, covered in Best Free PDF Tools and Office Alternatives for Windows.
  5. Check group policy. On a work machine open gpedit.msc and look under File Explorer for a setting turning off thumbnail caching. If the machine is managed, ask your IT department before changing policy.
  6. Repair the system if all else fails. A hanging Explorer slows preview loading too, see File Explorer Not Responding or Frozen in Windows 11, then run sfc /scannow to fix damaged files.

FAQ

Will clearing the cache delete my photos

No. It deletes only the preview cache Windows generated; your original photos, videos, and documents are untouched and previews rebuild when you open them again.

I cleared it and previews still will not show

Check that Always show icons, never thumbnails is unticked, or that group policy is not disabling them. If both are fine, restart Explorer and look again.

Videos show but PDFs do not

PDFs need a separate preview handler. Install Adobe, Foxit, or a similar reader to get previews; a plain image viewer usually does not include one.

Why are network and USB drives so slow

Generating a thumbnail there means reading the original file, so speed is limited by the transfer. Wait a while, or copy the files locally to browse them smoothly.

How It Works

A thumbnail is a small image Windows generates ahead of time and caches. When Explorer needs to show a preview, it calls the codec or preview handler for that file type, renders the content to a small image, and stores it in thumbcache_*.db for reuse.

That explains the failures. Tick Always show icons and Windows skips rendering and draws an icon directly; damage the cache and the stored small image comes back empty so it falls back to an icon; miss a codec for one type and only that type refuses to render while the rest work. See the generate plus cache chain and you know whether to fix a setting, clear the cache, or add a codec, rather than reinserting the USB stick again.

Conclusion

Thumbnails not showing usually comes down to three places: a setting turned off, a damaged cache, or a missing codec. Check the setting, clear the cache, then fill in the file types, and previews nearly always come back. Clearing the cache only removes Windows temporary small images and never touches your originals, so it is safe. Learn these three moves and the next time a folder turns into a wall of icons you will know exactly which one to reach for.