Where Does Finder Save its Thumbnails/Previews?

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Where Does Finder Save its Thumbnails/Previews?

Finder does a nice job of generating thumbnails for image files when you go into a folder containing images and have the appropriate view option selected. These thumbnails appear to be saved somewhere, since the first time you go into a folder you can actually see the thumbnails being generated, but thereafter, it is nearly instantaneous. I have googled and searched and hunted but I cannot find where Finder caches these things.

I have been using digital cameras for ever, and take a lot of photos. I would like to find this thumbnail cache so that I can purge it from time to time. If I am not able to do this, it will just get bigger and bigger and bigger, and this kind of "run away" data just makes me crazy.

Can someone point me at the location Finder uses to cache its thumbnails? Thanks!

Power Mac G5, Dual 2.3 GHz, Mac OS X (10.4.6), 2.5 GB RAM

Posted on Jun 13, 2006 12:48 PM

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Answer 1

Mulder

Level 6

8,990 points

Jun 13, 2006 1:09 PM in response to mac57

I don't think it does cache them; they're part of the file itself. If you have Photoshop or another image editor, you can choose whether or not to save the file with an image preview, so you could always open each file and save it again without that preview.

Mulder

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Answer 2

mac57 Author

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Jun 13, 2006 1:40 PM in response to mac57

I wish that were the case, but it is too fast for that. The first time through a folder you can see the thumbnails appear as they are read or generated. For all subsequent accesses, it is for all practical purposes, instantaneous. This survives across power down/power up of the Mac, and so it has to be stored on disk somewhere.

Now, just to add some spice to this, I tried it on removable drives and there it behaves just like you suggest - each time you mount the drive and view a folder of images, you can see it generate the thumbnails.

So, perhaps there is different treatment depending on whether you are on the system volume or some other volume? Is there some hidden file like .DS_Store lurking somewhere in my system volume, quietly accumulating thumbnails...?

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Answer 3

Mulder

Level 6

8,990 points

Jun 13, 2006 5:39 PM in response to mac57

If there is a cache, it's not doing any harm, since it doesn't build up just because you run your system. Whenever you add images, the cache would be added to, and if you remove images, the cache would get rid of that data.

.DS_Store files only track where thing are positioned on your system; they aren't caching anything.

Mulder

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Answer 4

Jun 14, 2006 12:27 AM in response to Mulder

.DS_Store files only track where thing are positioned on your system; they aren't caching anything.

I would have said that too, since as far as I know Finder doesn't keep any thumbnail caches. But the fact is that the first time you open a folder full of images without built-in thumbnails in icon view it takes a noticeable amount of time for Finder to draw them, but in subsequent openings they do indeed seem to appear as quickly as if they did have thumbs. I did a bit of experimenting and deleted the .DS_Store file in such a folder, and Finder did have to redraw the thumbs when I opened the folder later, and recreated the .DS_Store file. However, the file just isn't big enough to be a thumbnail cache. I would guess it does include some sort of instruction to the Finder about thumbs, but doubt it includes any actual thumbnails.

However, in my case this speediness does NOT persist through a restart.
Francine

Francine
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