User profile for user: mathewfromsanjose
mathewfromsanjose Author
User level: Level 1
9 points

iMac thumbnails not showing for JPG and ARW images on drives

This started happening recently (~1mo). I use an iMAC Retina 5K, 27-inch, 2019 running MAC OS Sequoia 15.8. I am a photographer and have thousands of images. On my internal and external drives, the thumbnails do not show always as images only a generic file icon. Some folders all files and in some a mix of images and the generic file icons. This makes it very time consuming to find photos. The images are .jpg and .arw file format. The .jpg taken by both an iPhone and Sony Cameras. I've been using this iMAC for 5-6 years and never before have I had this issue. I went through the regular recommended fixes for this but the problem persists. Please advise if you have any ideas to fix. Thanks.

iMac 27″, macOS 15.8

Posted on Sep 20, 2026 11:31 AM

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10 replies
User profile for user: Old Toad
Old Toad
User level: Level 10
218,318 points

Sep 20, 2026 4:24 PM in response to mathewfromsanjose

You'll probably have to do this with all of the folders on the external drives but try with the drive's top window itself and see if it will trickle down:


1 - wile in the Finder with an open external drive open select the View ➙ Show View Options menu option:


2 - in the View Options window click the checkbox Show Icon Preview at the bottom:



While there you can increase the font size and icon size.


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User profile for user: mathewfromsanjose
mathewfromsanjose Author
User level: Level 1
9 points

Sep 21, 2026 8:43 AM in response to Old Toad

Thank you Old Toad. Yes I gave that a try before asking for help on this forum. Unfortunately it did not help. I further searched this morning and did find a comment about a bug in Apple's release of macOS Sequoia 15.8:

Running macOS Sequoia 15.8 explains exactly why this is happening. You have run into a widespread known bug specific to the macOS 15.8 update.

This specific update introduced a regression that disrupts Apple's native RAW image handling. When Finder encounters a folder with camera RAW files (like .ARW, .CR2, .CR3, or .NEF), the background imaging service crashes. This crash instantly breaks thumbnail generation for all subsequent images in that session—which is why your PSDs and some of your JPGs are suddenly showing as blank or generic icons.

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User profile for user: Old Toad
Old Toad
User level: Level 10
218,318 points

Sep 21, 2026 9:59 AM in response to mathewfromsanjose

Give thia a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists.  Reboot normally and text again.


Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.


Then try the Icon Preview method again.


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User profile for user: E-P7
E-P7
User level: Level 1
8 points

Sep 26, 2026 1:45 AM in response to mathewfromsanjose

I just wanted to add that I too have the exact same problem in 15.8, RAW and Jpg.


Sequoia worked fine until I did the update.


Quicklook not working either.


I will be updating to MacOS 27 soon, but in the meantime I need to know that Capture One is okay.


M4 MacMini. 24gb RAM.


Can someone please post the direct link for reporting to Apple as we photographers need our Macs!

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iMac thumbnails not showing for JPG and ARW images on drives

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