How to fix the “Startup Disk Full” error on your Mac

12 min read

The limitedness of space on Mac has always been a problem. Another issue is the macOS itself. The modern macOS versions like Ventura and Sonoma are increasingly browser-oriented and aim to perform most of the work online. It for sure reduces the toll on your hard drive, and there may come a day when the message “Your startup disk is almost full” hits you hard. But how could a full startup disk affect you?

Let’s start with the beginning: what is a startup disk? Well, it’s the hard drive that contains your operating system, which makes it the most important disk of all. So, when the “Your startup disk is almost full” message pops up, it basically means you are running out of space on your primary disk drive, and that is very bad news. But we’ll show you how to fix that.

"Your disk is full" message

What does it mean when your Mac says the disk is full?

When a Mac startup disk is reaching full capacity, it is bad news for two reasons:

  • Soon, you’ll run out of space entirely.
  • A disk that is full (or even near full) is going to perform slowly.

What most people don’t realize is that their Mac actually converts the available space on their startup disk into virtual memory, which you use for day-to-day operations. Ideally, 10% of the disk should be free to leave your Mac’s OS enough space to operate. Therefore, if you’re running low on space, you’re heading for big problems.

How to check disk space on Mac

To get to the root of the problem and find the solution, you must discover what is taking up all the space on your startup disk drive. To have an overview of how your space is being used, simply follow these steps:

  • Click the Apple Icon.
  • Choose About This Mac.
  • Click More Info > Storage Settings. System Preferences - Storage

From here, you’ll be able to see exactly how much space you’ve got left and what’s eating up the used one. Luckily, your disk will be full of movies, photos, and audio. Why luckily? Because these files are easy to remove or move to another location. Any external drive or cloud storage will do the trick, and your Mac’s going to thank you for leaving it space to breathe.

However, there’s another scenario in which other data is taking up the free space, with files you cannot or do not want to delete. This situation’s a bit trickier, but don’t worry. Our 10 tips will surely give your Mac some extra space. So, let’s start fixing your Mac right now.

10 essential tips to clear the startup disk on a Mac

Believe it or not, one of your Mac’s occupations is to create junk. But don’t blame it; it’s just doing its job. macOS, like any other operating system, depends on creating temporary files, caches, and backups to perform correctly. However, after this data has done its part, it remains latent on your Mac, killing space for no purpose.

The good news is that it’s extremely simple to remove these useless files, freeing up gigabytes and fixing your startup disk full problem without affecting your personal data. So, here is how you can fix the “Your startup disk is almost full” error message by deleting the files you don’t need and never use.

1. Delete app cache (system junk)

The funny thing with cache files is that they are as necessary as they are useless. At first, caches serve a major purpose, as they get created in order to speed up processes. But once that process ends, you’re left with temporary junk generated by apps and system processes. Unless you remove them yourself, they will remain on your Mac for long. If you don’t, then these temporary files will become a permanent problem for your hard drive, as they will continue to pile up and make your startup disk full.

Fortunately, it’s an easy problem to solve simply by removing them. And don’t worry, your apps will soon refresh their caches and be back up to speed in no time.

To remove app cache files and clean up a startup disk, follow these steps:

  • Navigate to Finder and click Go > Go to Folder from the menu bar.
  • Type in ~/Library/Caches and press Return.Remove app cache on Mac.png
  • Go into each folder (or just the ones taking up the most space) and delete the files inside. Do not delete the folders.
  • Now, do the same for /Library/Caches (without the ~).Remove system cache on Mac

Note that there is always a small risk: when manually deleting files, you might pick the wrong folder. So, consider backing up these folders before you start deleting them.

Alternatively, you can clean up all caches in a fraction of the time and with 100% confidence if you download CleanMyMac X. This is how easy it is to delete tons of system junk at the same time using this flow:

  • Download CleanMyMac X and open the app.
  • Click System Junk.
  • Click Scan.
  • When the scan finishes, click Clean.

CleanMyMac X - System junk scan complete

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2. Take out the trash

Sometimes, we overlook the most obvious solutions because we think the fix must necessarily involve some complex operation. But when there’s not enough disk space, Mac can be saved through the simplest trick. 

The fact is that your Trash is a graveyard for files you no longer need. Still, these files keep taking up space on your Mac’s drive. So, you’ve probably guessed it: take out the Trash — just click “empty” to completely get rid of those piles of useless data.Empty Trash

We’re also going to satisfy your need for secret solutions by pointing out something you might not have thought about: every single app has its own trash folder that also stores useless gigabytes. The Mail app is one example, but there are many more. Just like the general Trash, you need to empty these folders in order actually to remove the junk and clear up disk space.

Once you empty all the trash folders in all the apps, you’ll be ready to move to the next tip. Ready? Let’s go.

3. Remove Time Machine backups

We love Time Machine because it creates important backups. But when your Mac can’t function due to a lack of disk space, there has to be a sacrifice. You can start with removing past Time Machine “snapshots” stored locally on your Mac. So, the first step towards removing the “startup disk full” message is to take care of these backups. Yes, by taking care, we mean removing them. To do it, all you need is to temporarily turn off your Time Machine.

  • Open System Settings > General > Time Machine.
  • If it is set up, click Options > Backup Frequency > Manually. System Preferences - Time Machine

Then, you should give it a few minutes to take effect. Your local Time Machine snapshots will be deleted.

4. Delete browser cache

Your internet browser creates caches every time you visit a new page to load it faster on your next visit. However, doing this literally for every page keeps your browser folder cluttered, creating an even bigger problem.

So, if you’re wondering how to safely clean a startup disk on Mac, removing browser junk is definitely a priority.

Every browser has a different cache removal process, so to remove unnecessary files, follow the steps below based on the browser you’re using.

How to delete cache in Safari:

  • Open Safari, click Safari in the menu bar > Settings.
  • Go to the Advanced tab and select Show features for web developers (Show Develop menu in menu bar in older macOS versions).
    How to empty cache in Safari
  • Open the Develop menu and then choose Empty Caches.
    How to remove cache in Safari

How to delete cache in Chrome:

  • Open Chrome and at the top right, click three dots > Settings > Privacy and security > Clear Browsing Data...
  • Select boxes next to Cached images and files. You can also select cookies and other site data.
  • Click Clear data.
    How to remove cache in Chrome

How to delete cache in Firefox:

  • In the menu bar at the top, click Firefox and go to Settings.
  • Select the Privacy & Security tab.
  • In the Cookies and Site Data, click Clear Data.
  • Select Cached Web Content and click the Clear button.
    How to remove cache in Firefox

But there is an easier and time-saving alternative to clear browser cache — CleanMyMac X. Simply go to the System Junk module, click Scan, and then Review Details. Then, click User Cache Files and click Clean. Done!

CleanMyMac X - User cache files in System Junk module

5. Remove language packs

Most of your apps come with language packs (also known as localization files) that enable you to change the language in the app. It’s great to have this option, but let’s face it: most people only need one language supported. Maybe two at most. The rest? They’re just wasting space.

To delete language packs manually, follow these steps:

  • Navigate to Applications.
  • Right-click (or ctrl-click) on an app and select Show Package Contents.
  • Click Contents > Resources.
  • Delete whatever languages (ending in .lproj) you don’t need.
  • Repeat for other apps.Removing language packages

An even faster way to remove language packs is to use CleanMyMac X’s System Junk module. After running the scan, you can click Review Details and find Language Files. Click it to see exactly what language packs will be removed. Once you’re happy with the selections, click on the big Clean button to further clear your startup disk.

6. Clear System Data storage

Mac System Data includes macOS system and temporary files, app extensions or plug-ins, old backups, cache files (system cache, browser cache, etc.), and others. You have to be very careful not to do any damage to the system when trying to clear those up by yourself. If you have no idea what you’re doing, then don’t! Otherwise, use Finder to delete System Data files from the Library folder on your Mac.

Follow these instructions to clear system data storage in Finder:

  • Open Finder > Go > Go to Folder.
  • Type in ~/Library and press Return.
    Clear system data storage on Mac
  • Go through each folder to find files you no longer need. Drag them to Trash.
  • Empty the Trash. Empty trash on Mac

7. Remove iOS backups

Do you own an iPhone or iPad? Have you ever updated those devices using your Mac? If the answer is yes, then you most likely have old backups taking up valuable space on your startup disk. The fastest and easiest way to delete heavy iOS backups is with macOS’ Optimized Storage feature. Here’s how:

  • Go to Apple menu > About This Mac > More Info > Storage Settings.
  • Look for iOS Files on the list and click the i icon next to it. You should see a list of iOS backups in the main window, together with their size and the date they were last accessed.
  • Select the backup you want to delete, then click Delete and confirm.
  • Repeat for each of the backups you want to delete.Remove iOS backups from Mac

8. Uninstall unused apps

How many apps do you have on your Mac? Let’s be honest: how many of them do you actually use?

Most people have at least a handful of apps that they never opened. You might think: so what? But these apps are wasting space, potentially even wasting other resources like RAM if running in the background.

So, take a moment and have a look through your applications to see if there are some apps you can let go of and remove for more space and speed. Dragging them to the Trash will uninstall the app, but it will also leave behind lots of hidden files associated with the app, like app logs and crash reports.

To see the list of all your unused apps and remove them completely, use CleanMyMac X’s Uninstaller module. For a hard disk, it is a great startup cleaner that will free up all of the space that apps are taking up on your Mac.

Unused Apps in Uninstaller module in CleanMyMac X

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9. Clean up your files

If, when checking what takes up storage on your Mac, you noticed that music, photos, and documents occupy a lot of space, it’s time to get rid of these files. Here are a few tips for you: 

  • Move files to an external hard drive or cloud.
  • Use built-in Finder tools to find the largest or oldest files and remove them once and for all. Simply open your target folder and use Size or Date Added filters to find these files. Or you can use CleanMyMac X’s Large & Old Files module to do the detective job for you.
  • Remove unneeded files from the Downloads folder. Do the same for Movies and Music folders and photo library in the Photos app. Finally, clean up your Desktop.
  • Remove duplicate files and photos from your Mac. For more information on how to find these files, check out this article.
  • Compress the largest files: just control-click files you want to archive and choose Compress. It works best for old videos or photos. 
    Compress files on Mac

10. Remove log files

Log files are plain-text files that record all events taking place on macOS and third-party apps. They may not take a lot of space, but deleting them is another way to fix the “Your startup disk is almost full” error. Just follow these steps: 

  • Open the Finder and click Go > Go to Folder. 
  • Type the following path: ~/Library/Logs and press Return. 
  • Delete those you no longer need.Remove log files on Mac

No more “Startup disk full” error message

When wondering how to free up space on a Mac startup disk, it’s hard to tell where to begin. With these 10 tips, you have everything you need to get rid of the “Your startup disk is almost full” message for good.

Certain tricks like deleting cache with CleanMyMac X and emptying your Trash should become part of your routine. This way, your startup disk will be able to focus entirely on smoothly operating your Mac. So, bookmark this page and use these tips regularly to ensure the problem never returns.

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