User profile for user: iJeffR
iJeffR Author
User level: Level 1
23 points

Hide File Extensions not maintained since Sequoia 15.4 upgrade on M1 Mac mini and M3 MacBook Air

Ever since I have upgraded to Sequoia 15.4 on both my M1 Mac mini and my M3 MacBook Air, Finder is not hiding file extensions.


I have navigated to Finder > Preferences > Advanced and toggle the "Show all filename extensions" option to off on both machines. I have also done "Get Info" on the individual files and clicked, "Hide Extensions". Then, when I come back, the extensions are back. These files are in my iCloud Drive.


While not a big deal normally, I don't like the extensions showing. This is happening on PDF files, XLSX files, as well as others.


All applications are up to date. The OS is up to date. This is either a bug in the updated OS, a bug in the PDF software and Microsoft software. Although all my years in IT tells me that when this starts happening with products from multiple vendors, then the common denominator, the OS, that was changed is most likely the cause.




[Re-Titled by Moderator]

Mac mini

Posted on Apr 7, 2025 6:49 AM

Reply
Question marked as Top-ranking reply
User profile for user: matthew stoops
matthew stoops
User level: Level 1
14 points

Posted on Apr 7, 2025 8:09 AM

The answer to the question is out there on the interwebs, but I'll share what worked for me. You need to be comfortable with the command-line, using the Terminal app (I recommend iTerm2, but I digress). There is a command called defaults that lets you make changes to the system defaults, without having to dig through app settings. It does come with its own learning curve, and you can always read about with man defaults in the terminal if you want to learn more about it.


The specific setting is the global attribute AppleShowAllExtensions, which should default to false. Unfortunately it seems to be getting stuck to true even if using the Finder's settings to change it. Since the attribute defaults to false, we can just "delete" it, which the Finder sees as "use the default." The command specifies the global context with the option "-g". Once the change is made you need to restart the Finder, which is what the killall command does; you should no longer see the extensions. Don't worry, the Finder automatically restarts.


defaults delete -g AppleShowAllExtensions && killall Finder


This has been bugging me for a while, finally realized that default was the answer, which I confirmed by a quick DuckDuck search to confirm I had the correct setting.

View in context
31 replies
User profile for user: VikingOSX
VikingOSX
User level: Level 10
123,290 points

Apr 7, 2025 8:59 AM in response to iJeffR

As a rule, I do not hide extensions. Several years ago, I wrote a voice-activated AppleScript solution that could hide or show a file extension on one or more selected files in the Finder. Got tired of talking to myself though.


Apple owns the operating system and the macOS team may have just decided in a vacuum to make the Finder retroactively show all hidden file extensions as a new macOS dogma. They could do that out-of-touch thing without an ounce of thought or remorse.


Been on all of the platforms you mention, for longer, and in developer, migration, and integrator roles. Lots of domestic and international travel thrown in to make things interesting.



Reply

This thread has been closed by the system or the community team. You may vote for any posts you find helpful, or search the Community for additional answers.

Hide File Extensions not maintained since Sequoia 15.4 upgrade on M1 Mac mini and M3 MacBook Air

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.
Learn more Sign up