Quick Look is one of the most beloved features in macOS. By simply selecting a file and tapping the Spacebar, macOS instantly generates a high-resolution preview of the document, image, or video without ever opening a heavy application.
To make this feature lightning fast, macOS constantly generates and stores tiny preview images in a hidden background cache. However, if this cache becomes corrupted or bloated, Quick Look will break. You might press the Spacebar and see a generic white loading icon, a completely blank window, or the preview window might take several seconds to render.
In this guide, you will learn how to use the macOS Terminal to forcefully clear and rebuild the Quick Look cache, instantly restoring its speed and functionality.
Step 1: Open the macOS Terminal
Because the Quick Look cache is a protected system directory, there is no graphical button in System Settings to clear it. You must use the command line.
- Press Command + Space to launch Spotlight Search.
- Type Terminal and press Return to open the application.
Step 2: Clear the Cache via Command Line
The command to clear the cache uses the qlmanage utility, which is the backend engine that powers Quick Look.
- Copy the following command exactly as written:
qlmanage -r cache - Paste it into your Terminal window.
- Press the Return key on your keyboard.
The command executes almost instantly. You should see a brief output message in the Terminal confirming that the cache was reset. It will usually say qlmanage: call reset on cache.
Step 3: Restart the Finder
While clearing the cache is usually enough, the Finder itself often holds onto the corrupted preview data in its active memory. To ensure the fix takes effect, you must restart the Finder.
You can do this directly from the Terminal while you still have it open.
- Type the following command:
killall Finder - Press the Return key.
Your screen will flash briefly, and any open Finder windows will close as the application restarts. The macOS dock may also briefly disappear.
Step 4: Test Quick Look
You can now close the Terminal application.
Open a Finder window, navigate to a folder containing several large images or PDF documents, select one, and tap the Spacebar. Quick Look should now instantly spring open with a crisp, fully rendered preview, entirely bypassing the corruption that was slowing it down.
As you continue to use your Mac, the operating system will silently rebuild a fresh, healthy cache in the background. If you ever experience sluggish previews again in the future, simply repeat this 10-second Terminal fix.