256 GB MacBook 如何設定，避免一年內用盡儲存空間

The MacBook Neo starts at $599 with 256 GB. The base MacBook Air has the same.

That’s plenty on day one. macOS takes about 25 GB, and you look at the 200-something GB left and think you’ll never fill it.

(I wrote this with help from an AI assistant. Every number is measured on my own Mac.)

I thought that too. My MacBook Air has a 245 GB disk. Today it has 4.13 GB free, and the biggest thing on it is not my photos or my projects. It’s a grey bar called “System Data” at 142.69 GB.

This post is the setup I’d do on a new 256 GB Mac, knowing what I know now. Most of it is free and built into macOS.

What actually fills a small Mac

Not what you’d guess. I measured mine folder by folder:

• App data, 39.31 GB. The private folders apps keep in ~/Library/Application Support: databases, offline content, downloaded models. It grows quietly, and it stays behind when you delete the app.
• Shared Library and Homebrew, 31.88 GB. That one’s on me. I’m a developer. If you don’t install command-line tools, yours will be small.
• System caches and temp files, 10.93 GB. macOS manages these. Leave them alone.
• Developer and AI caches, 7.8 GB. Package caches and AI models in hidden dot-folders.
• Caches, 4.11 GB. Safe to clear, but they regrow.

The lesson: on a small disk, the problem isn’t one big file. It’s a hundred apps each keeping “just a little” data.

Step 1: Ten minutes in System Settings, before you install anything

1. General › Storage. Turn on Optimize Storage (removes TV shows you’ve watched) and Empty Trash Automatically (deletes Trash items after 30 days).
2. Photos › Settings › iCloud › Optimize Mac Storage. If you have a big photo library and an iCloud plan, this alone can save tens of gigabytes. Full photos stay in iCloud and download when you open them.
3. iCloud Drive › Optimize Mac Storage (in System Settings › your name › iCloud). Old files you haven’t opened stay in the cloud.
4. Messages › Settings › General › Keep messages: 1 year. Years of videos people sent you add up. Only do this if you’re fine losing old threads, or if Messages in iCloud has them.

Step 2: Don’t back up your iPhone to the Mac

One iPhone backup can be bigger than everything else in your home folder. If you plug your phone in and Finder offers to back it up “to this Mac”, say no and use iCloud Backup instead.

Already have one? Open Finder, click your iPhone in the sidebar, then Manage Backups to see the size and delete old ones.

Step 3: Install fewer apps, and uninstall properly

Every app you try for a day leaves files in your Library folder after you drag it to the Trash. Settings, caches, sometimes gigabytes of downloaded content.

Two rules I’d follow on a new Mac:

• Try apps in the first week, then decide. Keep what you used. Delete the rest while you still remember what you installed.
• Remove the leftovers too. Look in ~/Library/Application Support, ~/Library/Caches and ~/Library/Containers for folders named after the app. Or use an uninstaller that does it for you.

To see the biggest folders yourself (this deletes nothing):

du -sh ~/Library/* ~/.[!.]* 2>/dev/null | sort -h | tail -15

One catch: du counts APFS clones at full size, so a folder can look far bigger than it really is. Check free space before and after you delete anything.

Step 4: Put big files somewhere else

• Videos and old projects: an external SSD. A 1 TB one often costs less than Apple’s storage upgrade.
• Downloads: sort by size once a month. Installers (.dmg, .pkg) are safe to delete after you’ve installed the app.
• Time Machine: plug in a drive in week one. It backs everything up, and it means you can delete with less fear.

Step 5: Watch the number, not the warning

macOS warns you when the disk is almost full. By then you have a few gigabytes and no idea what changed.

Write down your free space today. Check it once a month. If it drops 20 GB in a week, something changed that week, and you’ll know where to look.

What I use to keep an eye on it

Doing step 5 by hand got old, so I built Tidy Mac. Full disclosure: it’s my app.

It shows your free space in the menu bar, with a 7-day and 30-day trend. Its Home screen splits “System Data” into named parts, like the chart above. And Clean sorts caches into “Safe to clear”, “Worth a look” and “Kept”, so you don’t have to guess:

Everything goes to the Trash first, and History has Undo. It’s free to download and look around, and the first 500 MB of cleaning is free. After that it’s Pro, $9.99 once for 2 Macs. No account, and your files never leave your Mac.

You don’t need it to follow this checklist. Steps 1 to 4 are free and do most of the work.

How much free space does your Mac have right now? Tell me in the comments, with the size of the disk. I’m curious how fast everyone else’s fills up.