Unexpected FileVault activation after macOS Tahoe upgrade on Mac Studio

if I wanted to deactivate how long roughly would it take on a 4TB drive or would it be too much hassle ?

If your Mac supports Tahoe, then you either have a T2 Chip or Apple Silicon. Both will encrypt the drive regardless of FileVault status. FileVault just changes how the encryption keys are made available.

Turning it off will not decrypt the drive, so it will be almost instantaneous.

This article describes the disk encryption scheme and the subtle difference the File Vault (FV) setting actually makes.

Volume encryption with FileVault in macOS - Apple Support

My own - possibly flawed - interpretation is:

• On Apple Silicon (or Intel T2 Macs) the drive is ALWAYS encrypted.
• The FV “on / off” setting only impacts how the encryption keys are protected; specifically by adding a key encryption key tied to the user password. (Which also explains why the FV “on/off” is nearly instantaneous as the data disk contents aren’t actually being encrypted / decrypted)

This article from a couple of years ago also touches on the subject:

https://www.macworld.com/article/231249/how-to-find-your-filevault-recovery-key-in-macos.html

littletree77 wrote:

Upgrade from macOS Sonoma to Tahoe turned on FileVault by default (no user intervention during upgrade). Unfortunately it has prevented file operation in Finder from working properly (I have never turn on FileVault). So under System Settings > Privacy & Security > FileVault, I turned off the FileVault switch. File operation (moving files into folder) works after that.

No idea why Apple has to turn on FileVault by default for the macOS upgrade.

FileVault is on in all but name on Mac models with T2 and later. See the earlier part of this thread.

As for what is reported with Finder, that seems like an unexpected or unrelated problem, or some sort of corruption. Or maybe this involves trying to move files to protected locations.

Upgrade from macOS Sonoma to Tahoe turned on FileVault by default (no user intervention during upgrade). Unfortunately it has prevented file operation in Finder from working properly (I have never turn on FileVault). So under System Settings > Privacy & Security > FileVault, I turned off the FileVault switch. File operation (moving files into folder) works after that.

No idea why Apple has to turn on FileVault by default for the macOS upgrade.

Dan867 wrote:

I just upgraded to Tahoe and the same thing happened - it activated FileVault without asking. This had the bad (to me) side effect that it disabled auto-login. Apple needs to fix this.

Apple chose to turn FV on by default in Tahoe, presumably for the (slightly) increased security. There’s always a chance they will reverse their decision, but since they implemented the change I doubt they see anything that needs fixing. To have Apple consider your feedback, submit it here:

Feedback - macOS - Apple

Note that you can also simply go to System Settings > Privacy & Security > FileVault and turn it OFF.

littletree77 wrote:

Upgrade from macOS Sonoma to Tahoe turned on FileVault by default (no user intervention during upgrade). Unfortunately it has prevented file operation in Finder from working properly (I have never turn on FileVault). So under System Settings > Privacy & Security > FileVault, I turned off the FileVault switch. File operation (moving files into folder) works after that.

No idea why Apple has to turn on FileVault by default for the macOS upgrade.

submit your Apple Feedback here: Product Feedback - Apple

ValerieLynn4 wrote:

No, you can’t just turn it off. The switch doesn’t work. Note says file vault can’t be enabled (even though it is on by default) because automatic login is enabled. But the automatic login note says it cannot be enabled because FileVault is enabled. No work around that I can find.

I would never advocate or encourage automatic login. You are simple setting your self up for issues, now or in the future. Does not make good computer sense.

You can try from Terminal.app to see the statuses copy and paste:

fdesetup status

You can try disabling copy and paste:

fdesetup disable

if it kicks out an exit status error code, post it here for review...

As mentioned, internal storage encryption is always enabled on Mac with T2 and Apple silicon.

Enabling FileVault gives you the choice of keys, rather than using a generated key.

Page 119ff: https://help.apple.com/pdf/security/en_US/apple-platform-security-guide.pdf

T2 and the secure enclave with Apple silicon are analogous to the Trusted Platform Module, though with features including storage encryption.

As for using FileVault on a Mac with T1, that lacks dedicated key storage, as referenced on page 99 in the Platform Security document.

I just deactivated FileVault on my 2TB Mac Studio Max. It took less than a minute to decrypt. And yes, it’s bit concerning that FileVault was turned on by default without asking in Tahoe.

Unfortunately it has prevented file operation in Finder from working properly (I have never turn on FileVault). So under System Settings > Privacy & Security > FileVault, I turned off the FileVault switch. File operation (moving files into folder) works after that.

Turning FileVault on makes no changes to the encryption of the drive, so there is no way that is related.

"If you sign in to an Apple account as part of setting up macOS, FileVault now turns on automatically [...] But if you decline to sign in with an Apple Account during setup, just creating a local account, the macOS installer offers FileVault encryption, generating a recovery key that you can write down and store elsewhere, but it's possible to skip FileVault entirely"

https://arstechnica.com/gadgets/2025/09/macos-26-tahoe-the-ars-technica-review/#toc-h8

alistairmck wrote:

hi, I'm just after upgrading to macOS Tahoe from macOS sequoia on my M2 Mac Studio, I've never had FileVault activated in previous macOS's but as soon as I

installed macOS Tahoe FileVault was activated with no option during setup process

did it ask if I wanted to have it activated. if I wanted to deactivate how long roughly would it take on a 4TB drive or would it be too much hassle ?

thanks in advance

[Re-Titled by Moderator]

Original Title: macOS Tahoe FileVault

Yep that is the Apple way...I tried to dodge it myself, but there was no way to avoid on the installation process.

However—Simple enough to turn it off.

You can submit your Apple Feedback here: Product Feedback - Apple

[Edited by Moderator]

Dan867 wrote:

I just upgraded to Tahoe and the same thing happened - it activated FileVault without asking. This had the bad (to me) side effect that it disabled auto-login. Apple needs to fix this.

?

Are you saying you can not simply turn it off in System Settings...?

File a bug report / submit your Apple Feedback here: Product Feedback - Apple

roxola wrote:

I have attempted to deactivate on a fresh install. After the usual hurdles, the button just bounces blue again

You should contact Apple Support.

Barney-15E wrote:

FileVault just changes how the encryption keys are made available.

Would you mind expanding on that? I’ve had FileVault enabled on my Macs for years, so I didn’t notice anything with the macOS 26 upgrade. Currently the household is all on Apple Silicon now. What are the pros/cons of turning FV off vs. leaving it enabled? Thanks!