Normally when updating the system by default we use the downloads that Apple offers us through the Mac App Store, either for the applications themselves or the system itself. However, it may happen that one day the association that the system makes with the icons for use with the related application becomes corrupted, is incorrect, so a different icon will be assigned or not updated to the new icon of the application itself. .
Fortunately, all these problems have a simple solution that we can carry out with just using the terminal no need for third-party applications , the Cocktail or TinkerTool.
To open the terminal we will only have to press SHIFT + CMD + U on the desktop and once inside the Utilities folder look for the terminal and run it. At this point we will have two options, the first is for those users who are in a OS X version 10.5 or higher, in this way we will have to enter the following:
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system -domain user
This command will rebuild the icon database in relation to the association with the system, thus restoring the icons within OS X as they should appear.
In the second case, if we are in a OS X version 10.4 or lower, we must enter this command:
/System/Library/Frameworks/ApplicationServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
This operation can take from 10 seconds to even the occasional minute, it is important not to close the terminal until we see that the cursor blinks in its normal state, it would be at that point when the execution of said command would have finished to restore the icons.