---
id: mac-storage-basics.what-is-the-macos-category-in-storage-settings
url: https://storagestudio.us/faq/mac-storage-basics/what-is-the-macos-category-in-storage-settings
category: "Mac storage basics"
subcategory: "System Data and the storage categories"
question: "Why is the macOS category in Storage settings so big, and can I shrink it?"
alt_questions:
  - "macos storage category size"
  - "macos taking up 20gb"
  - "can I delete macos storage"
  - "why does macos itself use so much space"
  - "macos system size on disk"
short_answer: "It's the sealed, read-only macOS system and can't be trimmed. Shrink System Data, your apps and your own files instead."
tags: ["macos", "storage settings", "system"]
related: ["https://storagestudio.us/faq/mac-storage-basics/can-i-delete-old-install-macos-apps", "https://storagestudio.us/faq/mac-storage-basics/what-is-system-data-on-a-mac"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# Why is the macOS category in Storage settings so big, and can I shrink it?

The **macOS** category is the operating system itself — the sealed system volume with its apps, frameworks and fonts. Its size depends on the macOS version and isn't something you can trim; it's protected and read-only by design.

What you *can* control sits elsewhere: System Data, apps you installed, and your own files. Old **Install macOS** apps in your Applications folder are separate and can be deleted if you don't need them.

See [deleting old macOS installers](https://storagestudio.us/faq/mac-storage-basics/can-i-delete-old-install-macos-apps).