How to fix Mac Quick Look not working or previewing files on macOS

Summary

This guide helps you troubleshoot and resolve: How to fix Mac Quick Look not working or previewing files on macOS. Follow the steps below to fix the issue.

Common Causes

Quick Look is a built-in macOS feature that lets you preview files and documents by selecting them in Finder and pressing the Space bar. When it stops working, files may appear blank, fail to load, or refuse to generate thumbnails. In most cases, the issue is caused by a corrupted preview cache or a stuck Quick Look process, both of which can be resolved without affecting your personal files.

Quick Fix Steps

If Quick Look has stopped responding or previews are failing, try these steps in order before moving to the detailed instructions below.

1. Select the file in Finder and press Space to test whether Quick Look is responding.
2. Quit and reopen Finder using Option + Right-click the Finder icon in the Dock, then choose Relaunch.
3. Force quit the Quick Look process via Activity Monitor.
4. Rebuild the Quick Look cache using Terminal.
5. Restart your Mac in Safe Mode to clear stuck system caches.

Detailed Instructions

Step 1: Relaunch Finder

Finder occasionally holds onto a broken Quick Look state. Relaunching it forces macOS to reload the preview service.

1. Locate the Finder icon in the Dock.
2. Hold Option and right-click (or Control-click) the Finder icon.
3. Select Relaunch from the context menu.
4. Try selecting a file and pressing Space again.

Step 2: Force Quit the Quick Look Process

If relaunching Finder does not resolve the issue, the Quick Look background process (qlmanage) may be stuck.

1. Open Activity Monitor from Applications > Utilities, or search for it using Spotlight (Cmd + Space).
2. In the search field, type qlmanage.
3. Select the qlmanage process from the list.
4. Click the X button in the toolbar.
5. Choose Force Quit when prompted.
6. Test Quick Look again by selecting a file and pressing Space.

Step 3: Rebuild the Quick Look Cache

macOS stores preview thumbnails in a cache folder. If this cache becomes corrupted, previews may fail to generate or appear blank. Rebuilding it forces macOS to regenerate previews from scratch.

1. Open Terminal from Applications > Utilities.
2. Type the following command and press Return:

   qlmanage -r

3. Wait for the command to finish. You may see several lines of output as the cache is reset.
4. Close Terminal and test Quick Look in Finder.

Step 4: Manually Clear the Quick Look Cache

If the command above does not resolve the issue, you can delete the cache files manually.

1. Open Finder and click Go in the menu bar.
2. Hold Option and select Library from the dropdown menu. This reveals the hidden user Library folder.
3. Navigate to Caches/com.apple.QuickLook.thumbnailcache.
4. Move the contents of this folder to the Trash.
5. Empty the Trash and restart your Mac.

Step 5: Restart in Safe Mode

Safe Mode clears certain system caches and disables third-party extensions, which can help identify whether background software is interfering with Quick Look.

1. Click the Apple menu and choose Shut Down.
2. Wait at least 10 seconds for the Mac to fully power off.
3. Press the Power button, then immediately hold Shift.
4. Release Shift when you see the login window.
5. Log in and test Quick Look by selecting a file and pressing Space.
6. Restart your Mac normally to exit Safe Mode.

Troubleshooting

Quick Look Works for Some Files but Not Others

If Quick Look previews work for images but not for documents, spreadsheets, or PDFs, the relevant preview extension may be missing or corrupted.

• For PDFs, ensure Preview is installed. To set it as the default PDF viewer, select a PDF in Finder, press Cmd + I to open Get Info, expand Open with, choose Preview, then click Change All.
• For Microsoft Office files, install or repair Microsoft Office or Microsoft 365, as Quick Look relies on these apps for document previews.
• For proprietary file types, ensure the originating application is installed. Quick Look cannot preview formats it does not recognise.

Quick Look Opens but Shows a Blank or Black Window

A blank preview window usually indicates a graphics or rendering issue.

• Quit and reopen the affected application.
• Restart your Mac to reset the graphics stack.
• Check for macOS updates via System Settings > General > Software Update.
• If you use an external display, disconnect it and test Quick Look on the built-in screen.

Quick Look Crashes When Opening Specific Files

If Quick Look consistently crashes on a particular file, the file itself may be damaged.

• Try opening the file directly in its native application to confirm it is not corrupted.
• Copy the file to a different location and test the preview again.
• If the issue affects only one file, consider re-downloading or restoring it from a backup.

Quick Look Stops Working After a macOS Update

Occasionally, macOS updates can disrupt Quick Look behaviour. After a major update:

• Reboot your Mac to complete any pending update tasks.
• Run the qlmanage -r command in Terminal to refresh the cache.
• Install any available updates for third-party apps that provide preview extensions.

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