Know before your Mac runs out of space.
Disk Forecast sits in your menu bar, learns how fast your disk fills, and tells you the day it'll run out. When it's time to make room, it shows you exactly what's safe to clear.
0 stars on GitHubmacOS 14 or later · Apple Silicon and Intel · Notarized by Applebrew install --cask coreyhaines31/tap/diskforecast
A weather report for your disk.
Every hour, Disk Forecast checks how much space is free and keeps a daily history. After 3 days it can see your pace, and a straight line through the last 30 days tells you when you'll hit zero, while you still have weeks to act.
- Built from your own history. Your disk and your habits, not an average of other people's Macs.
- Weeks of warning, not minutes. macOS speaks up when the disk is already nearly full. Disk Forecast tells you while it's still your choice.
- Always in view. Free space lives in the menu bar, so a 30 GB surprise never sneaks up on you.
System Data, finally explained.
Storage settings shows a gray bar called System Data and stops there. Disk Forecast opens it up and gives every part a plain-English line: what it is, whether it's safe to touch, and the fix Apple's own tools offer.
Local Time Machine snapshots, simulator runtimes, purgeable space, Apple Intelligence models, the Spotlight index, Docker. Nothing runs until you confirm.
com.apple.TimeMachine.2026-10-05-083008.local
com.apple.TimeMachine.2026-10-05-093011.local
iOS 26.2 runtime: 8.4 GB
14 simulators: 10 GB
Siri TextToSpeech: 583 MB
Speech AutomaticSpeechRecognition: 428 MB
Photos MagicCleanup: 260 MB
Build Cache: 1.6 GB, 1.6 GB unused
Containers: 318 MB, 12 MB unused
Reclaim space you can actually spare.
The Cleanup window sorts what it finds by risk. Safe to clear is what rebuilds itself: package manager caches, app caches (never macOS's own), logs, Xcode build data, and build folders like node_modules in old projects. A project counts as old when nothing directly inside its folder has changed in 30 days, and you can change that in Settings.
Worth a look is what only you can judge: local AI models from Ollama, LM Studio, and Hugging Face, build folders in projects you're still working on, virtual machines, installers, big downloads. Every line says in plain English what you're looking at.
Trash, never delete
Every file it clears goes to the Trash. Change your mind and put it back.
Apple's own tools
System fixes run tmutil, mdutil, and xcrun simctl, the commands Apple ships. Never a mystery script.
Nothing without a yes
Every action shows what it will do, and the exact command it runs, then waits for you to confirm.
Careful where it counts.
A disk tool is only as good as its numbers. These are the parts you won't see, and the reasons you can trust what you do.
A fast scanner
Reads folders in bulk with getattrlistbulk on a pool of threads, so a rescan is something you just do.
Counted once
APFS clones and hard links share the same space on disk. Disk Forecast counts them once, so its totals aren't inflated.
Your home folder is enough
It works with access to your home folder. Full Disk Access is optional and adds the folders macOS guards. Cloud drives are never scanned.
Updates itself
Signed with Developer ID and notarized by Apple. New versions arrive through Sparkle, and you can turn automatic checks off.
One line with Homebrew
brew install --cask coreyhaines31/tap/diskforecast, or download the app from GitHub.
Stays on your Mac
No telemetry, no account. What it learns about your disk never leaves the Mac it's on.
How it stacks up.
What you get for free, next to the apps people usually reach for. Each one has a longer write-up: DiskBuddy, DaisyDisk, CleanMyMac, GrandPerspective.
| Disk Forecast | DiskBuddy | DaisyDisk | CleanMyMac | |
|---|---|---|---|---|
| Price | Free | $19 at launch, now $49 | $9.99 one-time | From $47.50 a year |
| Tells you when the disk will be full | Yesfrom your own daily history | — | — | — |
| System Data broken down | Yesin plain English, with Apple's fixes | Snapshots view | — | — |
| Deletes go to the Trash only | Yes | Yes | — | — |
| Developer and AI-model clutter | Yescaches, build folders, local models | Yeslocal LLM model finder | — | — |
| Source available | Yes, on GitHub | — | No | No |
| Telemetry | None | — | — | — |
“—” means we couldn't confirm it from the vendor's own materials as of October 2026. Competitor prices and features change; tell us if something here is out of date.
Free. Really.
No account, no trial, no subscription, no ads. Use it at home or at work, and read every line of how it counts.
Questions
Is it safe?
Yes. Files it clears go to the Trash, where you can put them back. The Safe to clear group only holds things that rebuild themselves, like caches and build folders. System Data fixes run Apple's own tools, like tmutil and mdutil, and every one asks you first.
Does it delete anything?
Not on its own. Files move to the Trash, and the space comes back when you empty it yourself. The exceptions are System Data fixes, like removing local Time Machine snapshots: there, Apple's own tool does the work, and only after you confirm.
Why does it want Full Disk Access?
It doesn't need it. Everything works with access to your home folder. Full Disk Access lets it measure the folders macOS guards, like Mail, Messages, iCloud Drive, and other apps' containers. Without it, those folders are skipped and their space shows up as unexplained. You can change your mind any time.
Does it scan Dropbox or Google Drive?
No. Cloud drives like Google Drive, Dropbox, and OneDrive are never scanned. Each one asks for its own permission, and their files mostly live online anyway.
What is System Data?
It's the catch-all bar in System Settings › General › Storage for everything macOS doesn't file under a named category. The big pieces are usually local Time Machine snapshots, purgeable space, simulator runtimes, caches, Apple Intelligence models, and the Spotlight index. Our guide walks through each one.
Why not the App Store?
App Store apps run in a sandbox that can't see most of your disk, so a disk tool there can't measure System Data or run Apple's fixes. Even DaisyDisk ships a separate direct download for that reason. Disk Forecast is signed and notarized by Apple, and installs from GitHub or Homebrew.
Is it really free?
Yes, at home or at work. No account, no trial, no subscription. The source is on GitHub, so you can read exactly how it counts and what it moves to the Trash.
Does more free space make a Mac run better?
Not much, and we won't pretend otherwise. On a Mac with an SSD, free space doesn't change how it runs until the disk is nearly full, when updates fail and apps can't save. Disk Forecast's job is to keep you well away from that point.
How accurate is the forecast?
It's a trend, not a promise, which is why it says “~”. It draws a straight line through your last 30 days of free space, so a big download or a cleanup moves it. The forecast appears after 3 days of history, and if your disk is filling by less than 100 MB a day, it just says “Not filling up.”
Which Macs does it run on?
Apple Silicon and Intel Macs running macOS 14 Sonoma or later.
Where do I report a bug?
GitHub Issues. Pull requests are welcome too.
Know before it's full.
Free. No account, no subscription.
macOS 14 or later · Apple Silicon and Intelbrew install --cask coreyhaines31/tap/diskforecast