Instructions: Fix QuickLook errors on macOS

The QuickLook feature in the Mac operating system macOS is a fine thing. By highlighting a file or folder and pressing the space bar (alternatively cmd + Y), the relevant content can be viewed without opening the actual program. Whether a Word document, Numbers table, PDF file or JPEG image, these and other files can be viewed in the quick view; as well as audio and video files. But sometimes there is a QuickLook error under macOS that slows down the Mac, falsifies the display of the data or has other negative consequences. Here you will find instructions on how to fix the errors on the Apple computer for each approach.

The solution for QuickLook errors can be a restart, but also uninstalling plug-in extensions. Here are the step-by-step instructions on how to fix QuickLook problems such as incorrect display or high CPU load.
The solution to QuickLook errors can be a restart but also uninstalling plug-in extensions. Here is the step-by-step guide to fix QuickLook Problems such as incorrect display or high CPU load.

Problem: QuickLook only shows file icon or nonsense

QuickLook normally displays the content of a file, i.e. the text from a doc, docx, pages-, PDF and / or txt file and so on. Even videos can be viewed with the macOS tool. However, if you press the spacebar or cmd + Y (perhaps with the alt key for full screen mode) on a file and only the file symbol with some information (file size, number of files in a folder, etc.) is displayed, there is an error in front. Also, if the file contents appear weird or random in QuickLook, this is not normal. In the event of these occurrences, look at the solutions shown below.

Problem: QuickLook takes a long time and leads to CPU load

Although QuickLook is a small-looking tool, it consumes quite a bit of processing power. After all, instead of using its traditional program (Word, Pages, Excel, Numbers, etc.) are displayed in a single floating window with exactly matching controls. And that should also be done very quickly. So do you notice that QuickLook or the file preview / icon preview on the desktop and in the Finder takes a long time and slows down the processor, then also check out the solutions below. Each guide aims at a specific point of the possible causes of errors. If QuickLook is slowing down your Mac and taking a long time to display, give it a try.

Solution: restart Finder / restart Mac

The first and easiest way to fix any QuickLook issues is to restart the Finder. For some problems this can be a solution, especially for one-offs. So if you have the problem for the first time that the quick view of files and folders gets stuck, only shows nonsense or leads to a high processor load, then proceed as follows:

  1. Save open projects and files (otherwise they could be lost)
  2. On the Apple menu Click () at the top left
  3. The menu item Quit imediately… click
  4. In the "Quit programs immediately" window from the list Finder choose file
  5. Click on the blue "Restart" button

This can fix acute QuickLook errors. If that is not yet the case, close all programs and windows, restart the Finder and then restart the Mac as well (shut down completely and start up again). If these steps do not lead to the desired success, continue with the following steps.

Solution: Empty the QuickLook cache / delete the folder in the library

Another, quite simple, solution is to clear the QuickLook cache memory. As with other programs under macOS as well as on other systems (app cache on the iPhone, for example), this approach can achieve great success. Because outdated or damaged display histories, which are actually supposed to make it easier to quickly display files that have already been viewed, can lead to the collapse of the Mac in case of doubt. So if you find QuickLook incorrect or the tool takes far too long to display data, proceed as follows:

  1. Opens the Finder or any folder
  2. Click in the menu bar above Go to
  3. Hold down the Option key (Alt) (Library appears as a list item)
  4. Click on the one called up in this way Library-Entry
  5. In the Finder you open the subfolder in the folder that has been opened Caches
  6. Finds the folder named qlmanage and
  7. Delete both folders and try QuickLook

Variation: Clear the QuickLook cache via the terminal

Don't you want to click around in folders, but are friends of Port-Commands, you can also use the Mac command console to clear the quick view cache. The procedure is faster, but of course not as clear as the above approach. Here are the short instructions:

  1. Open that MacOS Terminal (via Applications -> Utilities or via Spotlight)
  2. Give the following commands one:
    qlmanage -r
    qlmanage -r cache
  3. Confirm each with Enter 
  4. Closes the terminal 
  5. Try out QuickLook

The commands entered and executed individually with Enter should start with qlmanage: reset quicklookd and qlmanage: call reset on cache have been confirmed. As with the manual deletion of the QuickLook cache memory described above, the memory of the tool was cleared so that display and execution errors could or should be corrected.

Solution: Uninstall the faulty QuickLook plug-in

Another cause of QuickLook problems can be plugins, especially those from third-party providers. These are not bad per se, but after a macOS update or in a completely new version of the Mac operating system they may no longer be 100% compatible with the preview tool. So if you have installed extensions for displaying ZIP, FLV, XML, folders, source codes or the like, uninstall them one by one. If you have been able to find the culprit, you can reinstall the previously deleted ones. Of course, it is also possible that not just one, but several QuickLook plugins lead to problems and errors - especially after a system update.

Problems and Solutions: When the Mac goes on strike under Mojave

Solution: Do not show any symbol previews, just file symbols

What some may not know yet: the preview of the file contents in the symbols of files (small image preview for JPG, PNG, PSD, etc., text preview for DOC, DOCX, PAGES, etc. and so on) is generated via QuickLook. With multi-page text files and PDF documents, you can even scroll through the symbols. Audio and video files can be played back as a preview with a play button. It is logical that something like that demands the processor and leads to a corresponding CPU load. You should therefore deactivate the icon preview, especially on the desk and in folders that are often used or filled with many files. And this is how it works:

  1. Click on the Desk or open the desired folder
  2. Now click on in the menu bar presentation 
  3. Pick the point Show display options (alternatively key combination cmd + J)
  4. Unchecked Show symbol preview
  5. Keep the small window open and select further folders to adjust their settings accordingly (or select the display options there individually)

Since the preview views no longer have to be constantly loaded and kept ready for use (scrolling, playback, etc.), you save a lot of Mac computing power. 

A little tip: Use this procedure to also delete the QuickLook cache (see instructions above); so you play it safe and prevent possible consequential errors.

No change to be seen yet? Rebooting your Mac once can help!

If you have tried one or more of the above instructions and there is still no improvement in QuickLook, it may be useful to restart your Mac. The restart causes the system to be reloaded, new directories to be created and so on. Therefore, some changes, adjustments and improvements under macOS are only visible and usable when you shut down the Apple computer completely and then let it reboot. If there is still no improvement, try another solution from the offer above - or leave a comment with your problem.

Did the instructions on how to fix QuickLook errors help?

Could I help you with this guide or could these solutions and step-by-step instructions help you to solve your QuickLook problem? Feel free to leave a comment! If the problem persists, please describe it in detail; then I'll try to solve it together with you :) Otherwise, I would also like to recommend further reading for dealing with Mac and macOS: Tips, shortcuts, Ochsenkühn standard work and Power user manual.

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8 comments on “How-to: Fix QuickLook errors on macOS”

  1. Hi

    because it fits here, maybe I can get rid of my longstanding problem with Quicklook.

    Since several OS versions (I say since 10.10) the following is no longer possible:

    Images that are smaller than the screen format used are no longer scaled up in Quicklook as a slide show in full screen mode (except for the first image), ie to the maximum height or width.
    To do this, select the images in the Finder and press the space bar together with the Alt key.

    I contacted Apple Support about this, but got no answer, not even a confirmation. Pity!

    Then the following was added with the last Mojave update (10.14.5):
    Some mp4 videos start as they should, but switch to "black screen mode" after a few seconds. You do not stop what you can tell from the sound, and as soon as you briefly tap the mouse, the image reappears, but only for a few seconds.
    However, it does not affect all mp4 videos, but mov videos converted from them are also affected.
    Switching off sleep mode did not improve the situation either. And before I forget:
    These affected videos run perfectly under 10.14.4! I can only hope that this bug will be fixed in the last Mojave update in a few weeks.

    But maybe you will find a way to fix my problems or have some kind of contact to pass the bugs on.

    Thank you very much for your efforts.

    Many greetings.

    Manfred Bohm

    1. Hello Manfred! Thank you for your feedback signal. For me, that doesn't work with the ALT space bar either. Has the feature been removed and is it not a bug? I have little experience with MP4 videos. I always watch them with VLC. But that sounds like a bug at first. Unfortunately, I have no better contact with Apple than any other user ... for Apple, I'm only one of millions of users. ;-) But there is hope that everything will get better with macOS Catalina.

  2. Hi
    Unfortunately, the proposed solutions did not help me. For me it is getting worse and worse. At first only the quick look was no longer possible with the PNGs, now the PDFs are also affected and I also have the problem that my copy and paste from one program to another no longer works since yesterday.
    Restart, etc. I've already done everything. Maybe you still have an idea for me ...


    1. Hello Sabrina! I would restart the Mac, then hold down CMD + R and install macOS over it again. That solves some problems ... and none of your data will be lost.

  3. Another problem was solved for me with the restart. And although my Finder window always jumped back when I scrolled to the left in the column view. Super annoying and with a restart also no longer available. Thank you for the contribution!

  4. Also just noticed: If you have files on Dropbox and they are only displayed as a "link" (cloud cloud behind file), then of course only the icon is displayed and not the content of the file...

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