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Uh oh, Your Startup Disk is Almost Full! Here‘s How We Can Fix This

It‘s a normal day and you‘re happily using your Mac. Then suddenly – a frightening message pops up warning "Your startup disk is almost full!"

What does this mean? And how can you get things back to normal? Not to worry, friend, I‘ve got you covered!

In this guide, we‘ll walk through everything you need to know to troubleshoot and fix a full startup disk on your Mac.

Defining the Mac Startup Disk

First things first – what exactly is the "startup disk?"

This refers to the primary storage drive that contains your Mac‘s operating system, applications, and personal files. It‘s the crucial disk that boots up your Mac when you turn it on.

For most modern Macs like MacBook Airs and MacBook Pros, the startup disk is the built-in solid state drive (SSD). On iMacs and Mac Pros, you may have chosen or added your own internal startup drive.

But in all cases, this startup drive is the beats of your Mac‘s heart – without enough free space, your whole system suffers!

According to Surveys by CleanMyMac X, the average Mac has between 128GB to 512GB of storage space. Yet over time, your free space shrinks as all kinds of files accumulate on the startup disk.

Let‘s look at the main culprits that gradually consume your precious storage real estate:

  • Apps: Your programs like Photoshop, games, productivity tools, etc. take up huge amounts of space. The average app size is 150MB!

  • Media: Photos, videos, music, and downloads hog more and more gigabytes.

  • Documents: Word files, spreadsheets, PDFs, and other work files need space too.

  • Backups: Local Time Machine backups take up drive space to protect your data.

  • Cached files: Temporary cache files that help apps load faster pile up.

  • System data: Behind the scenes, macOS writes log files, indexes, crash logs, and other system data.

You can see how all this data being written to your startup disk causes it to fill up over the years. Next we‘ll look at how to see exactly where your storage is being used.

Checking Your Mac‘s Disk Usage

To get a handle on your Mac‘s disk usage, let‘s open up the handy About This Mac window:

Step 1) Click the Apple menu and choose About This Mac.

About This Mac menu

Step 2) Click Storage to see the storage breakdown.

About This Mac Storage tab

This graph gives you a bird‘s eye view of what‘s using up space on your startup drive. Now we can zero in on areas to clean up!

Tip 1: Offload Files to External or Cloud Storage

One of the easiest ways to open up startup disk space is moving files to external storage. This removes data from the primary internal drive to make room.

You have a few great options for adding external storage with your Mac:

  • External SSD or hard drive – Connect a portable external drive via USB or Thunderbolt. Then transfer files over to free up your startup disk.

  • Cloud storage – Services like iCloud, Dropbox, and Google Drive let you securely store files online.

  • SD cards – Use a cheap SD card and reader accessory to add external storage.

  • USB flash drives – Flash drives offer affordable external storage for your Mac.

  • Network-attached storage (NAS) – NAS devices hook up wirelessly to your network for easy access.

To compare major storage types:

Storage Type Speed Cost Per GB Size Range Use Case
HDD Slower Cheaper 500GB-16TB External storage
SDD Faster More expensive 128GB-8TB Boot drives
Flash drive Fast More expensive 16GB-2TB Transferring files
SD card Average Cheap 16GB-1TB Cameras, mobile storage

For a simple cloud solution, let‘s look at moving files to iCloud Drive in a few quick steps:

Step 1) Go to System Preferences > Apple ID and ensure you‘re signed into your iCloud account. This lets you access cloud document storage in iCloud Drive.

Step 2) Turn on the setting for Optimize Mac Storage. This automatically manages your local space by uploading older seldom-used files to iCloud.

Step 3) Select which folders you want to sync to iCloud Drive – like Documents, Photos, Mail, and more. Recent versions will stay in your File Explorer for quick access!

Once set up, iCloud seamlessly handles moving your files off your startup disk but keeping them available on demand. What a relief!

Tip 2: Empty the Trash Can

Here‘s one of the quickest fixes – make sure to regularly take out the Trash!

When you delete a file on your Mac, it gets put in the Trash can rather than removed right away. So the Trash icon becomes a sneaky storage hog.

The Trash sits in the bottom right corner of your Dock by default. Let‘s empty it:

Shortcut: Press Command + Shift + Delete to instantly dump the Trash.

Empty Trash keyboard shortcut

Right-click: Right-click the Trash icon and choose Empty Trash.

Empty Trash context menu

Empty the Trash regularly before it piles up and steals precious gigabytes!

Tip 3: Delete Unused Applications

Applications take up more storage real estate than almost any other file category on your Mac. Most apps range from 100MB to over 1GB in size nowadays.

Let‘s remove some apps you no longer need to reclaim startup disk space:

Step 1) Open About This Mac > Storage again and click Manage.

Step 2) Select Applications to view your apps sorted by size.

List of applications by size

Step 3) Look for any apps you don‘t need and drag their icons to the Trash. For example, remove games you stopped playing, niche productivity tools, or apps that came preinstalled.

Uninstalling unused programs is an easy way to get back gigabytes of precious disk space! You can always reinstall apps from the App Store later on.

Tip 4: Tidy Up Your Downloads Folder

Over time, the Downloads folder tends to get bloated with random files and installations. Let‘s clean it up:

Step 1) Go to Finder > Go > Downloads to open your Downloads.

Step 2) Choose View > Arrange By > Date Added to sort files by when they were downloaded.

Step 3) Look through old Downloads and trash any you don‘t need – such as obsolete installers, software, or trial versions.

Step 4) For files you want to keep, properly file them away in the correct folder according to type – Documents, Music, Photos, etc.

Organize Downloads folder

An organized Downloads folder avoids it endlessly filling up with random junk. A cleaned out Downloads gives you back lost disk space.

Tip 5: Remove Unnecessary Cache Files

Cache files help apps and websites load faster by storing temporary usage data. But caches easily grow huge and become storage hogs.

Let‘s clear out some cache clutter:

Step 1) Press Command + Shift + G to open the Go to Folder dialog.

Step 2) Type in the path to your Cache folder:


Hit Go to open it.

Go to Cache Folder

Step 3) Browse the caches from various apps. Select a cache folder and move it to the Trash to delete the whole thing.

Step 4) Empty the Trash to permanently erase the cache. macOS will recreate caches as needed.

Removing outdated cache files is an easy way to spring clean your startup disk!

Tip 6: Upgrade to a Larger Internal SSD

For MacBooks and iMacs with proprietary storage, one more advanced option is upgrading your internal solid state drive (SSD).

Companies like OWC provide SSD upgrade kits to boost Mac storage capacity. Replacing an old 256GB or 512GB drive with a 1TB or 2TB SSD provides much more headroom.

The process involves:

  • Backing up your data completely
  • Opening up your Mac to access the internal storage
  • Swapping in the new SSD module
  • Clean installing macOS

This is definitely more technical but worthwhile if you need maximum internal space. Just take precautions – data loss can occur if you aren‘t extremely careful!

Troubleshooting a Still-Full Startup Disk

Uh oh…even after trying all the tips, you still get the dreaded "Your startup disk is almost full" warning. Don‘t panic, we can handle this!

Here are more troubleshooting tips to rescue a stubbornly full Mac disk:

  • Check the Trash again – it‘s easy to overlook large files in there.

  • Look for any legacy junk files like old backups or archives taking up space.

  • Scan for duplicate files wasting space using a tool like Gemini 2.

  • Monitor disk usage with an app like DaisyDisk to pinpoint any abnormal storage hogs.

  • Search online for common culprits like Xcode ghosts, Analytics data, and more. These sometimes cling to your system mysteriously.

  • Try uninstalling and reinstalling any extremely large applications that may have corrupted files.

  • Back up your data and erase the startup disk to perform a completely fresh macOS install.

With a bit of dedicated spring cleaning and troubleshooting, we can get your precious Mac storage back under control in no time! Just follow the steps in this guide, and let me know if you have any other issues.

Now get out there and enjoy all that newfound disk space! 💻