File Explorer’s Preview pane in Windows 11 can stop working for a few different reasons. Some are simple settings toggles. Others are new security rules that block previews for files downloaded from the internet. Here’s how to get previews back, what’s changed in recent Windows updates, and when “it’s not broken”—it’s by design.

Windows 11 Preview pane: quick checks that fix most cases

  • Turn on the pane: Open File Explorer, select View on the command bar, then choose Preview pane.
  • Allow handlers: Go to Options (three dots) → Folder Options → View tab, and check Show preview handlers in preview pane. Click Apply.
  • Show thumbnails: In the same View tab, make sure Always show icons, never thumbnails is unchecked.
  • Restart Explorer: Press Ctrl+Shift+Esc → Task Manager → find Windows Explorer → right‑click → Restart.
  • Rebuild the thumbnail cache: Open Disk Cleanup, select your system drive, check Thumbnails, and run cleanup. Restart the PC.
Note: A few users report previews return only after unchecking “Show preview handlers in preview pane.” If the usual setting doesn’t help, try toggling it off, apply, then on again.

New in 2025: why internet downloads don’t preview anymore

Windows now blocks Preview pane rendering for files marked with the Mark of the Web (MotW)—a flag applied to content from the internet, email, or certain cloud sources. This change reduces the risk of silent network credential leaks initiated by preview handlers loading external resources. Microsoft documents this behavior in its support guidance on Preview being disabled for MotW files (support.microsoft.com).

What you’ll see: local files preview as usual, but files you downloaded may show no preview and prompt you to open them instead. That’s expected with MotW.

Unblock a trusted file (so it can preview)

If you’re confident a file is safe and you want it to preview in Explorer:

  • Right‑click the file → Properties.
  • Under the Security section, check Unblock, then click Apply.

To unblock a batch of trusted files with PowerShell:

Unblock-File -Path "C:\Users\admin\Downloads\*.pdf"
Tip: Adjust the path and extension for your use. Only unblock content you trust.

Fix PDF previews in File Explorer (Acrobat, PowerToys)

  • Acrobat Reader setting: In Adobe Acrobat Reader, open Edit → Preferences → General and enable PDF thumbnail previews in Windows Explorer. Restart File Explorer.
  • PowerToys add-on: Install Microsoft PowerToys and open File Explorer add-ons. Enable the PDF (.pdf) preview handler. Then restart File Explorer.

Either approach enables the system to render PDFs inside the Preview pane without opening a full viewer.

OneDrive and sync folders: check these options

If previews fail primarily in synced folders, the root cause is often thumbnail or handler settings rather than sync itself. Reconfirm that:

  • Preview pane is enabled under View.
  • Show preview handlers in preview pane is enabled (or try toggling it, then restarting Explorer).
  • Always show icons, never thumbnails is unchecked.

At-a-glance troubleshooting

Symptom Likely cause What to do
Preview pane shows nothing for files you downloaded MotW security block Unblock via Properties → Unblock, or use Unblock-File for trusted files
No previews anywhere Pane or handler disabled View → Preview pane on; Folder Options → View → check “Show preview handlers…”
Icons appear but no image/video previews Thumbnails disabled Folder Options → View → uncheck “Always show icons, never thumbnails”
PDFs don’t preview No PDF preview provider Enable Acrobat thumbnail previews or PowerToys PDF preview add-on
Previews intermittently fail Explorer cache or session issue Restart Windows Explorer; clear thumbnail cache via Disk Cleanup
Settings changes don’t stick Handler setting edge case Toggle “Show preview handlers…” off, apply, then on; restart Explorer

What to expect going forward

If you primarily work with local files, enabling the pane, handlers, and thumbnails typically restores previews. For downloads, the Preview pane now respects the MotW security model—expect to unblock only the trusted files you want to glance at in Explorer. If you need frequent PDF previews, enabling a PDF handler (Acrobat setting or PowerToys add‑on) is the most reliable long‑term fix.