Have you noticed that when you're browsing through folders on the Mac that icons are actually previews of images and even live playable videos? This sure makes the OS X Finder snazzy looking, but in some situations where tons of images and video files are contained within single folders, it can have the unwanted side effect of general sluggishness. A simple solution to that slowdown is to turn off the image and video preview generation of the Finder, both for icon thumbnails and for the Preview panel that appears in the Column view. This tip isn't necessary for the average Mac user, but it should be particularly valuable for people who work with very large images and video files as it will offer a nice performance boost to working with any such documents within the Finder.
Note that neither of these settings will impact the functionality of Quick Look, letting you still easily scan through pictures but having more direct control over what is loaded and when. In other words, system resources will only be used when Quick Look is activated on the files in question, not simply when opening a directory.
Turning Off Icon Thumbnail Previews in OS X Finder
This is easy to do and will stop all icon thumbnail generation of folder contents:
- Open any Finder window other than All My Files, and pull down the "View" menu, choosing "View Options"
- Uncheck the box next to "Show icon preview", then to apply this to change to all folders click the "Use as Defaults" button
This setting change is immediately visible whether any folder is using the icon view, list view, or column view, all icon previews immediately disappear:
This trick alone can offer a significant performance boost to Macs as we've mentioned before, particularly for older models, those without SSD drives, or those with less available RAM.
Disabling the Finder Preview Pane in Column View
Disabling the icon previews is good, but sometimes it's not enough and sometimes that's not the cause of the performance issue anyway. For those who use the excellent Finder Column view, the Preview panel column can often be the culprit because it draws even larger live thumbnails of images and videos, and though it may look gorgeous if you have a folder packed full of massive videos and images it's going to really take a toll to generate these.
- Open the folder you want to turn column previews off for, then pull down the "View" menu and select "View Options" again if it was closed already from the prior tip
- Uncheck "Show preview column" to disable the preview pane
- Optionally, check the box for "Always open in column view" to be sure the settings stay put
This one is a bit trickier because it must be turned off on a per-folder basis, there is no simple way to apply this to every column window. The good news is that the View Options window will stay open as you navigate to other folders to adjust their settings, just be sure to keep checking the "Always open in column view" box for each folder to apply the settings to, that way everything stays consistent. Regardless, the setting is immediately visible in the column view and the preview window disappears:
This tip idea comes as a response to an inquiry from reader Adam G., a photographer who noticed a significant performance degradation on his Mac when looking through folders full of large layered TIFF files. That slowdown is because OS X is actively generating both an icon thumbnail preview of the image and another image for the Preview pane.
For what it's worth, boosting system RAM and upgrading to an SSD drive can improve the performance of background tasks like this considerably. Also, don't forget to check out our past guide on speeding up old Macs, though many of the tips are aimed at less powerful Macs, they certainly help to speed up new ones too.