Is macOS stored on hard drive?

MacOS, Apple’s operating system for Mac computers, is primarily stored on the hard drive. When you install macOS on a Mac, it takes up a significant amount of space on the hard drive. This includes the core operating system files as well as pre-installed applications like Safari, Mail, Calendar, Photos, and more. However, not every component of macOS is stored locally on the hard drive.

Where is macOS stored?

The primary location where macOS system files and applications are stored is in the /System folder on the startup drive. This is usually the internal hard drive on a Mac. For example, if your startup drive is named “MacIntosh HD”, the path would be /System on MacIntosh HD. This folder contains critical system files and frameworks needed for macOS to operate.

In addition to the /System folder, macOS also installs applications into the /Applications folder on the startup drive. This includes default apps like Safari, Mail, Calendar, Photos, GarageBand and more. User-installed apps also go in this folder.

Some supporting application files are stored in the user’s home folder Library. This includes things like application preferences, caches, and application support folders. So while the core apps and system files are on the hard drive, some supporting components are kept in the user’s profile.

The macOS installer itself is approximately 8-10 GB in size depending on the version. Once installed, a base installation of macOS Big Sur takes up around 20 GB of drive space. With additional apps and user data, macOS can occupy 50 GB or more of hard drive space.

What about iCloud?

While the main macOS system files and apps reside on the hard drive, some things are stored on Apple’s iCloud service. This includes items like:

  • User settings and preferences synced across devices
  • Photos and videos stored in iCloud Photos
  • Documents synced to iCloud Drive
  • Keychains and passwords stored in iCloud Keychain
  • Mail, calendars, contacts, bookmarks synced from iCloud

So even though the core OS lives on the hard drive, many personal data points are synced with iCloud. This provides redundancy and gives users access to their data across multiple devices logged into the same iCloud account.

Is the entire OS on the hard drive?

While most macOS system files and apps reside on the hard drive, some components are internet-based and stored in Apple’s cloud infrastructure. For example:

  • App Store app downloads and updates
  • iCloud syncing and storage services
  • Push notifications for apps and services
  • Siri voice assistant requests
  • Maps data and locations

So the full macOS experience involves both local hard drive storage and internet-based features and data. But the core operating system and included apps are stored locally on the hard drive when the OS is installed and updated. The main system functionality does not require internet access.

Why is macOS installed on the hard drive?

There are a few key reasons why Apple stores macOS on the hard drive rather than relying fully on the cloud:

  • Performance: Reading data from a local SSD or HDD is much faster than retrieving it from the internet. This provides a smooth and responsive user experience.
  • Reliability: Users can boot up and operate their Mac even without an internet connection, since the OS is installed locally.
  • Security: Keeping sensitive system files on the encrypted hard drive rather than in the cloud reduces exposure to hacking and malware.
  • Backwards compatibility: Newer macOS releases still support operating fully from a hard drive like older Macs without internet.

So while cloud integration provides helpful syncing and storage capabilities, Apple uses the local hard drive as the home base for macOS due to performance, reliability, and security considerations.

Is macOS installed differently from other operating systems?

The way macOS is installed and stored follows a similar approach to other desktop operating systems like Windows and Linux. The key similarities include:

  • OS installer is downloaded as a disk image or bootable external drive
  • Option for clean install, upgrade install, or dual boot
  • Core system files stored on the primary hard drive
  • Applications installed to program files folder on primary drive
  • Settings and user data stored separately from system files
  • Encrypted and permissions-based file system for security

macOS differs in some ways, however:

  • Simple, streamlined OS installer with little customization compared to Windows
  • No ability to install to secondary internal drive – only external drives
  • Tight hardware/software integration with Mac hardware
  • Seamless integration with iCloud cloud storage and sync

But overall, the approach of installing the OS to the primary hard drive with applications is the norm across operating systems. Apple sticks to this standard approach with macOS.

Does the recovery partition play a role?

Macs also include a small hidden recovery partition on the primary hard drive that stores recovery and reinstallation tools for macOS. This lets you boot to recovery mode to reinstall the OS, troubleshoot issues, restore backups, and more. So while not part of the main OS, the recovery partition complements it by providing restoration capabilities.

The recovery partition stores a copy of the macOS installer as well as tools for partitioning, time machine restores, internet recovery, and more all independent of the main operating system. This way you can troubleshoot and reinstall the OS even if the main hard drive partition becomes corrupted or unbootable.

So while not part of the primary macOS system, the recovery partition plays an important complementary role as a backup tool for recovery and reinstallation.

Can you run macOS from an external drive?

While the standard approach is installing macOS on the internal hard drive, it is also possible to install and run macOS on an external USB or Thunderbolt drive. This allows testing out the OS, keeping a portable bootable backup, or adding extra storage.

When installing macOS on an external drive, the same process occurs – the OS, apps, and libraries get copied to the external drive. You can then choose the external drive as the startup disk and boot directly to macOS from there. All installed apps and data will be on the external drive.

One catch is you cannot install macOS across multiple volumes – it has to reside entirely on one internal or external drive. But otherwise the external installation functions just like the regular internal hard drive OS.

This approach lets you take your entire macOS environment with you and boot it on any compatible Mac. The OS functions normally, just running off the external rather than internal drive.

Does iCloud make hard drive storage less necessary?

While iCloud provides helpful complementary cloud storage for backups, syncing and continuity, it does not eliminate the need for local hard drive storage. iCloud has storage limits from 5GB to 2TB depending on the plan, so it cannot mirror the full contents of a Mac’s massive internal SSD.

Also, iCloud is focused on user data like photos, documents, settings, etc. It does not contain the full macOS installer or all the system frameworks and libraries – that still resides primarily on the hard drive. Finally, booting and running macOS still requires the speed and reliability of the local solid state drive.

So while invaluable, iCloud does not provide a full replacement for local hard drive storage. It syncs and makes select data available across devices, while macOS needs a fast, reliable local hard drive as its home base.

Can macOS run from a network storage drive?

While macOS is designed to run from the local hard drive, it is possible to install macOS on network-attached storage (NAS) or a storage area network (SAN). This requires creating a virtual macOS boot environment on the network storage drive.

There are some key limitations to be aware of with this approach:

  • Speed will be slower than an internal SSD since network drives have slower access.
  • Drivers may be needed for your specific NAS/SAN hardware.
  • Booting directly from the network share will likely not be possible.
  • Ongoing compatibility issues as macOS updates could break things.

So while possible for experimentation, macOS is not designed to run long-term from networked storage. The official and supported approach is installing natively to an internal or directly-attached external hard drive.

Can I pick where macOS gets installed?

The macOS installer does not provide an option to select which physical hard drive volume you want to install the OS on. It will automatically install to the current boot volume.

To choose a different volume, you would first need to format and partition the drive as desired. Then boot to the macOS installer from the desired volume that you want the OS on. The installation would then put macOS onto that current startup drive.

Some options for selecting a volume include:

  • Install to external USB/Thunderbolt drive – Boot from it while running installer
  • Install to secondary internal drive – Make it startup drive then install
  • Install to partition – Create partition, make it active, boot from it

While less flexible than a Windows install, these options allow you to target where macOS get installed. But the installer itself provides no builtin way to redirect from the current startup disk.


In summary, while macOS integrates with internet services for syncing and storage, the core operating system and included apps are stored locally on the hard drive. MacOS relies on this high-speed, reliable local storage for critical system files and bootup. While components like iCloud provide helpful additional capabilities, the full OS foundation remains firmly rooted in the internal hard drive. This local storage, combined with Apple’s tight hardware-software integration, is what enables the smooth, polished macOS experience.