The Mac Library folder: what's inside and what's safe to touch

The Mac Library folder is where macOS and your apps keep the files that make them work: caches, settings, app data, logs, your mail and messages, fonts and more. Apple describes it as the place apps store their own data files, and asks you not to keep your own documents there.

There are three of them. The one in your home folder, ~/Library, holds your account's app data, and Finder hides it. The one at the top of the disk, /Library, is shared by every user. And /System/Library belongs to macOS alone, on a sealed volume that only Apple's signed updates can change.

Very little of it is yours to manage by hand. Folders inside Caches and files inside Logs are safe to clear; Application Support and Containers need a decision; Mail, Messages, iCloud Drive and Keychains are managed in their own apps. The Library folders themselves, and anything in /System, are never to be deleted.

This post shows how to open each one, takes a tour of what's inside, and points to what's safe to touch, with links to the detailed posts on the folders that take the most space.

What is the Mac Library folder?

Every Mac has at least three folders named Library. They hold the same kinds of things, but for different owners, and macOS treats them differently.

Why are there three Library folders?

Apple's documentation for developers splits the Mac's files into domains. The user domain is your home folder, which you control. The local domain is shared by everyone on the Mac and managed by administrators. The system domain is Apple's, and nobody can add, remove or change its items.

Each domain has its own Library folder, and apps put their files in the one that matches who should see them.

Library folder	Whose files	Who can change them	What it mostly holds
~/Library	Yours, for your account	You	Your apps' caches, data, settings, logs, mail and messages
/Library	Shared by every user on this Mac	An administrator	Shared app data, fonts, sound libraries, helpers and drivers
/System/Library	macOS's own	Only macOS	The system's frameworks, services, fonts and downloaded parts

Apple's guide also describes a network domain, for resources shared across an office network. You're unlikely to meet it on a Mac at home.

What is the Library folder for?

Apple's developer guide says the Library folder is where apps and other code store their custom data files: data, caches, resources and preferences. Each app is meant to keep its files in its own subfolder, named after the app or its bundle identifier.

Apple's user guide adds one rule for you: don't use the Library folder to store files and folders you create. Your own work belongs in Documents and the other folders in your home folder.

Is the Library folder part of System Data?

Mostly, yes. Storage settings has no line for the Library folder. It sorts what's inside into categories, and anything without a better one lands in System Data.

A few parts get their own category. Mail's folder counts under Mail, Messages' attachments under Messages, iPhone and iPad backups under iOS Files, iCloud Drive's local files under iCloud Drive, and GarageBand and Logic sounds under Music Creation. Caches, Application Support, Containers and logs count as System Data.

How to open the hidden Library folder

Your own Library folder is hidden in Finder. The one at the top of the disk isn't, and the System one is visible but locked.

Why is the Library folder hidden?

Apple's developer documentation notes that since Mac OS X 10.7 Lion, Finder hides the Library folder in your home folder. Apple's guides don't give a reason. The effect is that you're less likely to change files your apps depend on by accident.

Hidden doesn't mean protected. Once you open it, you can change and remove most of what's inside, so it pays to know what each folder does first.

How do you open the Library folder once?

1. Click the desktop, so you're in Finder.
2. Press and hold the Option key, and open the Go menu.
3. Choose Library, which appears only while Option is held.

A Finder window opens on your Library folder. It stays open until you close it, and the folder stays hidden in your home folder.

How do you open it with Go to Folder?

In Finder, choose Go › Go to Folder, type ~/Library and press Return. The tilde stands for your home folder. Go to Folder doesn't care whether a folder is hidden.

As you type, Finder suggests matching folders, and Tab accepts a suggestion. You can type deeper paths too, such as ~/Library/Caches, to go straight to one folder.

How do you show the Library folder all the time?

1. In Finder, choose Go › Home.
2. Choose View › Show View Options.
3. Select Show Library Folder.

The Library folder then appears in your home folder like any other. The setting belongs to your home folder's view options, so the checkbox appears only while your home folder is the front window.

How do you open /Library and /System/Library?

The shared Library folder isn't hidden. Choose Go › Go to Folder, type /Library and press Return, or open your startup disk, usually called Macintosh HD, and open Library there.

/System/Library opens the same way, from the System folder on the startup disk. You can look, but you can't change anything inside.

Way in	Opens	Changes a setting?
Option, then Go › Library	~/Library	No
Go › Go to Folder, then ~/Library	~/Library, or any folder inside	No
Show Library Folder in View Options	~/Library, shown in your home folder	Yes, until you turn it off
Go › Go to Folder, then /Library	The shared Library folder	No
Macintosh HD, then System, then Library	/System/Library	No

A tour of your own Library folder

Open ~/Library and you'll see dozens of folders. On the Mac running macOS 27 that we checked, there were more than 90. Most are small, and a handful hold almost all the space.

Here are the ones worth knowing, grouped by what they're for.

Caches

~/Library/Caches holds data apps keep so they can load things faster: thumbnails, downloaded web content, compiled code. Apple's guidance to developers is that it should hold only what an app can easily create again, and that apps shouldn't rely on cache files existing.

The folders inside are safe to clear with their apps closed; the Caches folder itself stays. A few apps keep more than a cache there, and the post on whether Library caches are safe to delete lists the exceptions.

Application Support

~/Library/Application Support is where apps keep the files they manage for you: libraries, databases, downloads, templates and settings. It's often one of the largest folders in the Library, and some of what's inside is your own work.

iPhone and iPad backups live here too, in MobileSync.

Containers and Group Containers

Sandboxed apps, which include most apps from the App Store, keep their files apart from the rest of your Library. macOS gives each one a container in ~/Library/Containers, with a Library of its own inside. Apps from one developer that share data use a folder in ~/Library/Group Containers.

Both hold data, settings and caches, and sometimes documents you saved only in an app.

Preferences and Saved Application State

~/Library/Preferences holds each app's settings, as small files ending in .plist. Apple tells developers not to write there directly, but through the system's preferences interface. Saved Application State holds the windows an app reopens after you quit or restart.

Both are tiny. Removing them frees almost nothing and resets the apps that own them, so they're never worth clearing for space.

Logs

~/Library/Logs holds log files that apps and macOS services write, and you can read them in the Console app. Its DiagnosticReports folder holds the reports macOS saves when an app crashes or hangs.

Nothing needs these files to work. Remove the files inside, not the folders, which some background jobs expect to find. The Console app can move crash reports to the Trash for you.

Mail and Messages

~/Library/Mail holds Mail's copy of your email, with a folder for each account. ~/Library/Messages holds your conversations and, in Attachments, every photo, video and file sent or received.

Mail keeps an index of its files, and Messages files attachments in coded folders only it understands, so removing files in Finder leaves gaps in your mail and conversations. Delete messages and attachments in Mail and Messages instead.

Mobile Documents and CloudStorage

~/Library/Mobile Documents is iCloud Drive's folder on your Mac, including the iCloud folders apps use. ~/Library/CloudStorage holds the folders of Dropbox, OneDrive, Google Drive and similar apps.

Deleting a file in either deletes it from the cloud and from your other devices. To free space on this Mac only, Control-click files in Finder and choose Remove Download, or the cloud app's own option, such as Make online-only.

Keychains

~/Library/Keychains holds your keychains: saved passwords, certificates and keys. It's small, and it's one of the few folders where removing anything can lock you out of accounts and apps.

Manage passwords in the Passwords app, or certificates and keys in Keychain Access. Never move keychain files to free space.

LaunchAgents

~/Library/LaunchAgents holds small files that tell macOS to start an app's helper when you log in, such as an updater or a sync tool. Apple's guide describes it as where agent apps are specified, to run for the current user.

The files are tiny, but a helper of an app you've removed may keep trying to run. Turn those off in System Settings › General › Login Items & Extensions, under App Background Activity.

Developer

~/Library/Developer holds Xcode's build files, simulators, device support files and archives. Apple's guide describes it as data used by Xcode and other developer tools.

On a developer's Mac, it's often the largest folder in the Library. Some of it rebuilds by itself, and some of it, such as archives, may be the only copy.

Fonts, Sounds and the small folders

Many folders hold a few kilobytes or megabytes: Fonts for fonts you installed only for yourself, Sounds for alert sounds, Keyboard Layouts, Screen Savers, ColorPickers, Services and more.

They're too small to matter for space. If you want to remove a font, do it in Font Book, which knows which fonts are installed where.

Folder in ~/Library	Who manages it	Where to manage it
Caches, Logs	Apps and macOS services	Finder, folders and files inside only
Application Support, Containers	Each app	The app, or its uninstaller
Mail, Messages	Mail and Messages	Those apps
Mobile Documents, CloudStorage	iCloud Drive and cloud apps	Remove Download in Finder, or the app
Keychains	macOS	The Passwords app and Keychain Access
LaunchAgents	Apps' helpers	Login Items & Extensions in System Settings
Fonts	Font Book	Font Book
Developer	Xcode	Xcode's own windows and settings

The folders with names you won't recognize

Next to the folders above, your Library holds many whose names explain nothing. That's normal, and most of them belong to macOS.

Why do some folders have names like com.apple.something?

Those are bundle identifiers, written backwards like a web address: com.apple for Apple, com.developer.appname for others. Apps name their folders this way so they never clash, and the developer part usually tells you who made it.

The same identifiers appear inside Caches, Application Support, Containers and Preferences. Once you know an app's identifier, you can find most of what it keeps on your Mac.

What are folders like Biome, Trial and DuetExpertCenter?

They belong to macOS services. On the Mac we checked, the Library also held folders named Biome, Trial, IntelligencePlatform, PersonalizationPortrait and UnifiedAssetFramework, among others.

Apple doesn't document most of them for users. They're managed by macOS, and some are protected from other apps. Leave folders like these alone, whatever their size.

What about folders named after apps you've deleted?

Dragging an app to the Trash removes the app, not its folders in the Library. Its caches, data, container, preferences and helper files can stay for years.

Caches and logs of a removed app are safe to clear. Its data folders need a look first, because they can hold work you made in it. The guide to uninstalling apps properly lists every place an app leaves files.

Why are there folders from command-line tools?

Developer tools often keep caches and data in your Library too: package managers, language runtimes, build tools. Some put them in Caches or Application Support; others use a folder at the top of the Library under their own name.

These follow the same rule as everything else: a cache can go, and anything that might be the only copy needs a check. Where a tool has its own cleanup command, that's the better way to clear it.

The shared Library folder at the top of the disk

/Library holds what apps install once for everyone on the Mac. Apple's guide says users with administrator privileges can add, remove or change items there, so most changes ask for an administrator's password.

What's inside /Library?

Many of the same folder names appear here, holding shared versions of the same things:

• Application Support, with data apps share between users, such as GarageBand's and Logic's sound libraries.
• Caches and Logs, used by helper tools, installers and some macOS services.
• Fonts installed for every user, and Audio for plug-ins, loops and drivers.
• LaunchAgents and LaunchDaemons, which start apps' helpers for every user or as system background jobs.
• PrivilegedHelperTools, where apps install helpers that need extra permissions.
• Developer, with Xcode's simulator runtimes and the Command Line Tools.
• Updates, which Software Update uses for update information and downloads.

What's safe to change in /Library?

Less than in your own Library. Caches and logs here can be cleared, with an administrator's password, and a service using its cache may only rebuild it after a restart. Shared sound libraries are best removed through Music Creation in Storage settings.

Helpers in LaunchDaemons and PrivilegedHelperTools belong to apps, and removing them by hand can leave an app half working. Use the app's uninstaller, or turn the helper off in Login Items & Extensions.

Why can't you change /Library/Updates?

System Integrity Protection protects it, so only Software Update can change it. The catalog entry for Software update downloads explains why it's usually small, and why installing a pending update is the way to let macOS clear it.

Folder in /Library	What it holds	What to do
Application Support	Data shared between users, such as sound libraries	Use the app, or Music Creation in Storage settings
Caches, Logs	Shared caches and logs	Clear what's inside, with an administrator's password
LaunchAgents, LaunchDaemons	Instructions that start apps' helpers	Turn helpers off in Login Items & Extensions
PrivilegedHelperTools	Helpers with extra permissions	Use the app's uninstaller
Developer	Simulator runtimes and the Command Line Tools	Manage simulator runtimes in Xcode
Updates	Software Update's files	Leave to Software Update

The System Library folder

/System/Library is macOS itself: the frameworks apps are built on, core services such as Finder, the system's fonts, sounds and desktop pictures, and parts of macOS downloaded after installation. Apple's guide says it's reserved for Apple.

Can you delete anything in /System/Library?

No. System Integrity Protection protects /System, along with other system locations, and only processes signed by Apple can change them.

Since macOS Big Sur, the system also lives on a signed system volume. Apple's security guide explains that macOS 10.15 moved system content to its own read-only volume, and macOS 11 added a cryptographic seal: the Mac rejects anything there without a valid signature from Apple.

Why does /System/Library seem to take space?

The sealed system volume is a fixed size, and it changes only when macOS updates. Storage settings counts it under macOS, which you can't change.

One part does grow: /System/Library/AssetsV2, where macOS keeps parts it downloads as features need them, such as speech and language data, voices, dictionaries and Apple Intelligence's models. The catalog entry for macOS downloaded assets covers it: macOS downloads, updates and removes them itself.

Can you turn System Integrity Protection off to make room?

Don't. It protects the parts of macOS that malware targets, and turning it off frees no space by itself. Guides that ask you to turn it off to delete system files are a reason to close the page.

What takes up space in the Library folder

On most Macs, a few folders in the Library hold almost all of its size. Which ones depends on how you use the Mac.

Which Library folders are usually the largest?

• Caches in ~/Library2–30 GB · Safe
• Logs and crash reports0.1–5 GB · Safe
• Shared caches in /Library1–10 GB · Usually safe
• Xcode DerivedData, in Developer5–100 GB · Safe
• Docker's disk image, in Containers10–100 GB · Usually safe
• GarageBand and Logic sounds, in /Library2–70 GB · Usually safe
• Messages attachments5–100 GB · Review first
• iPhone backups, in Application Support10–200 GB · Review first

Typical ranges on Macs that have these items at all, from the research behind the app's catalog. Many Macs have far less, and some have none.

The pattern is clear. The parts that are always safe to clear, caches and logs, are rarely the largest. The largest parts, backups, attachments and app data, are the ones that need a decision.

How do you find the largest folders in your Library?

1. Open your Library folder with one of the ways above.
2. Choose View › as List, then View › Show View Options, and select Calculate all sizes.
3. Click the Size column heading to put the largest folders first.
4. Open the largest and repeat, until you reach a folder whose name tells you what it is.

Finder takes a while to add up big folders, so let the sizes fill in. For one folder, select it and choose File › Get Info.

What does that look like in practice?

Say Storage settings shows a large System Data figure, and you open your Library folder to see why. With Calculate all sizes on, three folders stand out: Application Support, Containers and Caches.

Inside Application Support, the MobileSync folder holds two iPhone backups, one of a phone you sold last year. You delete that one under iOS Files in Storage settings rather than in the Library, so the backup goes as a whole.

The largest container belongs to a virtual machine app you still use, so you remove an old machine inside the app instead. In Caches, two folders belong to apps you removed months ago: those go to the Trash. The rest stay, because their apps would only rebuild them.

The backup was most of the space. The caches freed a little, and nothing in Preferences, Keychains or the com.apple folders needed touching.

Why do different tools show different sizes?

A disk tool that macOS doesn't let read every folder shows protected ones as smaller or empty. Recent versions of macOS keep apps' containers and some apps' data from other apps, as the section on macOS 27 and macOS 26 explains.

Other figures can differ too. Some files share space through APFS clones, and some, such as Docker's disk image, report a size larger than the space they take.

Why does my Library folder keep growing?

Because every app you use adds to it, and few remove what they no longer need. Caches grow with use, apps' data grows with your libraries and histories, and folders of deleted apps stay behind.

A quick look every month or two, at the largest folders only, catches most of it. Clearing everything at once rarely helps for long: caches come back as soon as you use the apps.

What's safe to touch in the Library folder

The short answer is: the contents of a few folders, never the folders themselves. The long answer depends on what each folder holds.

What	Level	Why
Folders inside ~/Library/Caches	Safe	Apps create them again
Files inside ~/Library/Logs	Safe	Nothing needs them to work
Folders inside /Library/Caches	Usually safe	Needs an administrator; services may need a restart
Application Support, Containers	Review first	May hold your own work
Mail, Messages	Review first	Change only in Mail and Messages
Mobile Documents, CloudStorage	Usually safe	Deleting deletes everywhere; remove the download instead
Preferences, Keychains	Not for space	Tiny, and removing them resets apps or locks you out
/System/Library	Managed by macOS	Sealed and protected by macOS

The post on what's safe to delete on a Mac goes beyond the Library, folder by folder across the whole disk.

Is it safe to delete the Library folder?

No. Your Library folder holds every app's data and settings, your mail, messages, keychains and iCloud Drive files. Moving it to the Trash would reset every app at once and could lose data that exists nowhere else.

The same goes for the folders directly inside it, such as Caches, Application Support and Containers. Clear what's inside them, item by item; never the folders themselves.

Can you move the Library folder to an external drive?

No. macOS and apps look for your Library in your home folder, and moving it, or a folder inside it, makes apps start fresh with new, empty folders.

Some apps that keep large data have their own setting for where it goes, such as a virtual machine app or a music app's sound library. When an app offers one, use it.

Should you clear Preferences to fix an app or save space?

Not for space: the files are tiny. Removing an app's preferences resets it to how it was when you first opened it, which occasionally fixes a problem but also loses every setting you chose.

If an app misbehaves, look for its own reset option or ask its developer first. If you do remove its preferences file, quit the app, move the file to the Trash, and keep it until you're sure.

Mistakes to avoid in the Library folder

Most damage in the Library comes from cleaning in bulk, or from following advice written for a different version of macOS.

Clearing folders by name alone

A folder called com.apple.something isn't safe to remove just because you don't recognize it, and a large folder named after an app you use daily isn't spare space just because it's large. Check what a folder belongs to before you remove anything, and leave what you can't identify.

Emptying the Trash straight away

Move things to the Trash and leave them there for a few days. If an app turns out to need something, choose File › Put Back. Emptying the Trash is the one step you can't undo without a backup.

Pasting Terminal commands

Guides that ask you to paste a command to clear the Library remove files with no Trash, no undo and no chance to check them first. Fake cleanup guides are also a known way to install malware. Everything in this post works in Finder and in the apps themselves.

Following old advice

Older guides suggest clearing whole folders that macOS now manages, or changing system folders that are now sealed. On macOS 26 and macOS 27, those steps either fail or do harm. Check the date and the macOS version of any guide before following it.

Restoring something you removed by mistake

If you've emptied the Trash and use Time Machine, open the same folder in Finder with Go › Go to Folder, then open Time Machine and go back to a backup from before the removal. Select the folder and click Restore, with its app closed.

Library folders on macOS 27 and macOS 26

Recent versions of macOS have tightened which apps can read which parts of your Library. That changes what disk tools and other apps can see, not what you can do in Finder.

What changed for containers?

Since macOS Sonoma, macOS links each app's container to the app, and asks you before another app reads it. On macOS 26 Tahoe, you may see a prompt saying an app would like to access data from other apps.

Apple's release notes for macOS 27 Golden Gate say that accessing files in other developer teams' app containers and group containers no longer prompts you. Such access is denied by default, and you can manage it in Privacy & Security settings.

What does XProtect protect now?

The same release notes say XProtect may now restrict access to app data that malicious software commonly targets, and access to files created by other developers' apps may be denied by default.

The Eclectic Light Company found that the list covers folders in Application Support for Chrome, Brave, Edge, Firefox, Discord and a few cryptocurrency wallets.

For those apps, clear caches and data in the app's own settings, on macOS 27 and macOS 26 alike. It's the safer route anyway.

Do disk tools need Full Disk Access?

To measure everything in your Library, a disk tool or backup app usually needs Full Disk Access, in System Settings › Privacy & Security. Without it, protected folders show as smaller, empty or unreadable.

Give it only to apps you trust and that need it to do their job. Full Disk Access doesn't change what macOS protects in /System.

How the app does it

Wombit scans your Library folders like the rest of the disk, reading only names, sizes and dates, and shows them in its map with everything else. Select a folder, and it says what the folder is and how safe it is to remove, from a catalog of rules with sources.

Folders macOS didn't let it read are listed, not skipped. Items no rule explains get a Best guess, written on your Mac by Apple Intelligence and labelled as a guess, and they're never offered for removal.

The Library folders themselves are never removed, and neither are keychains, iCloud Drive and other cloud folders, or anything in /System. Items inside get one of four levels: Safe items such as app caches start checked; Usually safe and Review first items wait for your choice; Managed by macOS items are explained and never moved.

• ~/Library/Caches/*

  App caches

  Data that apps and macOS services keep so they can load things faster. Apps create it again when they need it.

  Safe · Moves it to the Trash

• ~/Library/Application Support/*

  Application Support folders

  Data that apps create and manage for you, such as libraries, databases, downloads and settings, in a folder for each app.

  Review first · Explained only: the app shows you how

• ~/Library/Containers/*

  App containers

  The private folder a sandboxed app, such as most apps from the App Store, uses as its own home for data, settings and caches.

  Review first · Explained only: the app shows you how

• ~/Library/Mobile Documents

  iCloud Drive

  The iCloud Drive files that are downloaded to this Mac, including the iCloud folders that apps use.

  Usually safe · Explained only: the app shows you how

The analyzer, the map, the explanations and System Data explained are free. Cleanup, Trash first, with a review sheet and a log, is PRO, one payment of $4.99 with lifetime access. File names and paths never leave your Mac.