Disk Forecast

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Disk Forecast sits in your menu bar and shows how much space is free. After a few days it knows your pace and tells you when the disk will be full ("Full in ~41 days · using 3.5 GB a day"), shows which folders are growing, and clears what's safe to clear. It's free, the source is on GitHub, and nothing about your disk ever leaves your Mac.

It's a free alternative to DiskBuddy, DaisyDisk, and CleanMyMac for the job they're most often bought for: getting disk space back.

What it does

• Forecasts when your disk fills. Free space is checked every hour and saved once a day. The forecast follows your typical daily change over the last two weeks, so one big download or cleanup doesn't throw it off.
• Shows the trend. A small chart at the top of the menu, and a Forecast window with 2-week, 30-day, and 4-month views, the projected full date, and the lowest point.
• Says what changed. After each scan it saves folder sizes, so it can show which folders grew since any day in the chart, down to the subfolder that did it.
• Explains System Data. Local Time Machine snapshots, purgeable space, the Spotlight index, simulators, Apple Intelligence and Siri models, and Docker, each with a fix that uses Apple's or the tool's own command.
• Reclaims space safely. Caches (including the ones VS Code, Cursor, Slack, and Figma keep with their data), logs, Xcode leftovers, package manager caches, what coding agents leave behind (npx packages like MCP servers, Playwright and agent-browser browsers, older Claude Code versions, and temp files from Claude Code sessions idle for 2 days, which can reach tens of gigabytes), build folders in old projects, and git's records of deleted worktrees are listed as Safe to clear. Big downloads, disk images, VMs, local AI models, editor data for deleted projects, and git worktrees left by coding agents (each with what removing it would lose: changed files, commits no remote has) are Worth a look and never selected for you. Files go to the Trash, where a cleanup can be undone, or, if you choose Delete Immediately, are deleted right away. Anything a running app still has open is left alone, with the app named so you can quit it.
• Warns you before the disk fills. A notification when the forecast says full within a week, or space runs low, naming what grew most this week and how much emptying the Trash would get back. At most once a day, and you can turn it off in Settings.
• Works from Terminal. The diskforecast command gives you, or an AI agent, the forecast, what changed, and the cleanup list.
• Counts accurately. APFS clones and hard links are counted once, so totals match what the disk really spends.
• Zero telemetry. Checking for updates is the only time it goes online.

Install

Requires macOS 14 Sonoma or later, on Apple silicon or Intel.

Homebrew:

brew install --cask coreyhaines31/tap/diskforecast
open -a "Disk Forecast"

Or download: get DiskForecast-<version>.dmg from Releases, open it, and drag Disk Forecast to Applications. Then open it from Applications.

Or ask your coding agent. Paste this into Claude Code, Codex, or another agent that can run commands on your Mac:

Install Disk Forecast, a free macOS menu bar app (https://github.com/coreyhaines31/diskforecast), on this Mac:

1. Check that macOS is 14 or later with `sw_vers -productVersion`. If it's older, stop and tell me.
2. If Homebrew is installed (`command -v brew`), run:
   brew install --cask coreyhaines31/tap/diskforecast
   Otherwise, install the latest release from GitHub:
   url=$(curl -fsSL https://api.github.com/repos/coreyhaines31/diskforecast/releases/latest | grep -o 'https://[^"]*\.dmg' | head -1)
   curl -fsSL -o /tmp/DiskForecast.dmg "$url"
   mnt=$(mktemp -d) && hdiutil attach -nobrowse -quiet /tmp/DiskForecast.dmg -mountpoint "$mnt"
   cp -R "$mnt/Disk Forecast.app" /Applications/ && hdiutil detach -quiet "$mnt" && rm /tmp/DiskForecast.dmg
3. Check it's notarized: `spctl --assess --type exec -v "/Applications/Disk Forecast.app"` should say "Notarized Developer ID".
4. Open it: `open -a "Disk Forecast"`.
5. Open the Full Disk Access settings for me:
   open "x-apple.systempreferences:com.apple.preference.security?Privacy_AllFiles"
   Then tell me to turn on Disk Forecast there (it's optional), that its drive icon with my free space is now in the menu bar, and that from now on I can ask you why my disk is filling up or what's safe to clear. You'll use the `diskforecast` command (see `diskforecast --help`; if it isn't on the PATH, it's at "/Applications/Disk Forecast.app/Contents/MacOS/diskforecast").

Don't change any other settings and don't delete anything.

The app is signed with a Developer ID and notarized by Apple, so it opens without warnings. It updates itself through Sparkle. It isn't on the App Store because the App Store's sandbox can't measure the whole disk.

First run

1. Open the app. It has no Dock icon. Look for a drive icon with your free space (like 142 GB) in the menu bar, near the clock.
2. Choose how much it can see. A window asks for Full Disk Access. It's optional:
   • Open System Settings → turn on Disk Forecast under Privacy & Security › Full Disk Access (click + and choose it from Applications if it isn't listed) → come back. The app notices on its own.
   • Continue with home folder only to measure just your home folder. Folders macOS guards, like Mail, Messages, and other apps' containers, are skipped and show up as unexplained space.
3. Allow Desktop, Documents, and Downloads if macOS asks. Without Full Disk Access, macOS asks once for each of these folders. Click Allow so they're included.
4. Wait for the first scan. The menu shows Measuring… N files while it works. A home folder with a few million files takes one to two minutes. After that it scans twice a day on its own.
5. Leave Launch at login on. It's on from the first launch, so the daily readings keep coming after a restart. You can turn it off in Settings… › General.

What to expect over the first days:

When	What you'll see
Right away	Free space, the folders taking the most space, and how much is Safe to clear
Day 2	The chart has its first line
Day 3	The forecast: "Full in ~41 days", "Steady", or "Free space growing"
After scans on two different days	What changed in the Forecast window, and "Grew most this week" in the menu

Using it

Click the menu bar item:

• Free space and the forecast at the top, with a Low on space warning when you're under 10% (or 20 GB) free. Click the warning to open Cleanup.
• The chart. Click it, or choose Forecast…, to open the Forecast window.
• Taking the most space: the five biggest folders. Each one lists what Cleanup knows inside it, which opens Cleanup at that item, and Show in Finder. When Cleanup doesn't know a folder, Suggest a Rule… opens a GitHub issue filled in with its location and size, for you to edit and send.
• Safe to clear: 12 GB… moves everything in the Safe to clear group to the Trash, after a confirmation that lists what's included.
• Open Cleanup… to review both groups and pick exactly what to move. Copy Agent Prompt copies what you picked as instructions for a coding agent like Claude Code or Codex instead: only those paths, each checked first, with git checks before a checkout goes.
• System Data… to see what macOS counts as System Data and fix the parts you can.
• Rescan to measure again now.

Getting the space back. Moving files to the Trash doesn't free space until the Trash is emptied. The menu shows what's in the Trash (Empty Trash: 8.4 GB…), and emptying it from there works even on items Finder gives up on, like folders whose path is too long. Emptying needs Full Disk Access. If the disk is too full to use the Trash at all, the result offers Delete Instead.

System Data fixes run real commands, like tmutil deletelocalsnapshots or xcrun simctl runtime delete. Each one shows the exact command and asks you to confirm. Some ask for your administrator password.

Settings:

• General: Launch at login · what the menu bar shows (free space, percent free, or icon only) · automatic update checks.
• Scanning: Full Disk Access status · how long a project must be untouched before its build folders count as Safe to clear (30 days by default) · Rescan Now.

Command line

The diskforecast command reads the forecast, what changed, and the cleanup list from Terminal, so you, a script, or an AI agent like Claude Code or Codex can answer "why is my disk full?" and reclaim space without clicking through the menu. There's a friendlier walkthrough at diskforecast.com/command-line.

diskforecast status                 # free space, the forecast, and what's safe to clear
diskforecast changes --days 30      # which folders grew, down to the subfolder that did it
diskforecast cleanup                # what you can reclaim, with an ID and an explanation for each
diskforecast trash xcode-derived-data package-caches        # shows what would move
diskforecast trash xcode-derived-data package-caches --yes  # moves it to the Trash
diskforecast undo                   # puts back everything the last trash run moved

• status shows free space, the forecast, a low-space warning, and how much is Safe to clear.
• changes compares the folder sizes saved after each scan, over the last 7 days or --days N. It also shows how much changed outside your home folder (System Data, other accounts, and apps).
• cleanup lists the same items as the Cleanup window, grouped into Safe to clear and Worth a look, each with an ID, its size, and why it's listed.
• trash takes item IDs or paths from the cleanup list. Without --yes it only shows what it would move. It refuses anything that isn't on the list, and like the app it only ever moves things to the Trash. Empty the Trash to get the space back.
• undo puts back everything the last trash run moved, whether it ran from Terminal or the Cleanup window. If an app has already made a new folder in the same place, that item stays in the Trash.
• scan measures again (--wait waits until it's done), and open forecast, open cleanup, open system-data, or open settings shows a window.
• Add --json to any command for output a script or agent can read. If Disk Forecast isn't running, the command opens it in the background.

Installing the command: Homebrew links it for you. If you installed from the DMG, open Settings… › General and click Install… next to diskforecast command (macOS asks for your password), or link it yourself:

sudo mkdir -p /usr/local/bin
sudo ln -sf "/Applications/Disk Forecast.app/Contents/MacOS/diskforecast" /usr/local/bin/diskforecast

If you installed with Homebrew before the command existed, run brew reinstall --cask diskforecast once to link it.

For AI agents: paste this into Claude Code or Codex, or add it to your CLAUDE.md or AGENTS.md:

When my Mac is low on disk space, use the `diskforecast` command (run `diskforecast --help`). Start with `diskforecast status` and `diskforecast changes --days 30` to explain what's filling the disk, then `diskforecast cleanup` to see what can be reclaimed. Show me what you'd move and ask before running `diskforecast trash <id> --yes`. Never delete files directly.

Use Disk Forecast from Claude Desktop

Download diskforecast.mcpb and double-click it (or drag it onto Claude Desktop) to install the Disk Forecast extension. Then ask Claude things like why is my disk full?, what filled it up this month?, or what can I safely clean up?

The extension runs the diskforecast tool from your installed Disk Forecast app, so install Disk Forecast first. It only reads: Claude can't move or delete anything through it. The source is in mcpb/; cd mcpb && npm install && npm run pack builds mcpb/dist/diskforecast.mcpb, and npm test calls every tool on your Mac.

Privacy and safety

• Disk Forecast reads file sizes and names. It never reads file contents.
• Nothing about your disk is sent anywhere. The only network request is the update check, which fetches a small feed from this repo's GitHub releases. You can turn automatic checks off in Settings.
• Files go to the Trash unless you choose to delete them, and every deletion asks first. It refuses anything outside your home folder, your home folder itself, and the standard folders in it (like Documents or Library).
• It never scans cloud drives (iCloud Drive, Dropbox, Google Drive), so it never downloads cloud-only files.
• Its history lives in ~/Library/Application Support/Disk Forecast/.

Troubleshooting

I can't see it in the menu bar. On a MacBook with a notch, macOS hides menu bar items that don't fit. Quit an app or two, or ⌘-drag other icons out of the way. Then ⌘-drag Disk Forecast where you want it. If it's not running, open it from Applications.

It's been "Measuring…" for a long time. macOS may be waiting on a permission prompt (Desktop, Documents, or Downloads). Look for the prompt and answer it. Folders still waiting after a few seconds are skipped and measured on their own, so the rest of the scan finishes.

Its numbers don't match Finder or Storage settings.

• Purgeable space: Finder and Storage settings count purgeable space as available. The System Data window shows how much of it there is.
• Clones and hard links: Disk Forecast counts these once, so a folder full of APFS clones can look smaller here than in Finder. That's the space the disk actually uses.
• Home folder only: without Full Disk Access, guarded folders aren't measured.

I cleared space but free space didn't go up. Empty the Trash. If it still doesn't go up, local Time Machine snapshots may be holding the deleted files. You can see and remove them in System Data….

It says "Forecast ready in 2 days". It needs three daily readings. Keep it running (leave Launch at login on) and the forecast appears.

How do I update? It checks for updates on its own. You can also choose Check for Updates… from the menu, or run brew upgrade --cask diskforecast.

How do I uninstall it? Quit it from the menu, then either:

brew uninstall --cask --zap diskforecast

or move Disk Forecast from Applications to the Trash, then remove ~/Library/Application Support/Disk Forecast and ~/Library/Preferences/app.diskforecast.DiskForecast.plist. Remove it from Full Disk Access in System Settings too, if you added it. If you linked the command yourself, also run sudo rm /usr/local/bin/diskforecast.

Something else? Open an issue.

Building from source

Requires Xcode 16 or later and XcodeGen.

git clone https://github.com/coreyhaines31/diskforecast.git
cd diskforecast
brew install xcodegen swiftlint
xcodegen generate                 # creates DiskForecast.xcodeproj from project.yml

Run the tests (no signing needed):

xcodebuild -project DiskForecast.xcodeproj -scheme DiskForecast \
  -derivedDataPath build/DerivedData CODE_SIGNING_ALLOWED=NO test
swiftlint --strict

Build an app you can run on your own Mac, signed locally instead of with a team:

xcodebuild -project DiskForecast.xcodeproj -scheme DiskForecast \
  -derivedDataPath build/DerivedData DEVELOPMENT_TEAM="" CODE_SIGN_IDENTITY="-" build
open "build/DerivedData/Build/Products/Debug/Disk Forecast.app"

In Xcode, open DiskForecast.xcodeproj, choose your own team (or "Sign to Run Locally") under Signing & Capabilities, and run.

A development build uses the same app ID and data folder as the installed app, so quit one before running the other. Full Disk Access is granted per copy of the app.

Where things live:

• Packages/DiskForecastCore: the scanner, forecast, cleanup catalog, Trash rules, folder snapshots, and System Data parsers, with unit tests. Most logic changes happen here.
• DiskForecast/: the app. The menu, windows, and settings (AppKit and SwiftUI).
• site/: the website at diskforecast.com, generated by python3 site/_build/render.py.
• Scripts/: the release script and the icon renderer.

See CONTRIBUTING.md before opening a pull request. Maintainers: releases are covered in RELEASING.md.

License

FSL-1.1-MIT © Corey Haines. Free to use and modify, including at work. You can't resell it or build a competing product from it. Each release becomes MIT two years after it ships.

The Disk Forecast name and icon are covered by the trademark policy.