To free up disk space, it’s helpful to know exactly what is using disk space on your Mac. A hard disk analysis tool like Disk Inventory X will scan your Mac’s hard disk and display which folders and files are using up the most space. You can then delete these space hogs to free up space. If your Mac is running out of space after checking the disk space on your Mac, just try MacClean to free up more disk space on your Mac. If you have any questions, please let us know in the comment section.

If you’re looking for solutions on how to fix ‘startup disk full’ error on your Mac or simply want to clean or optimize your storage space, you’ve come to the right place. Although the newest models of Apple computers are now equipped with relatively large hard drives, some users still find themselves dealing with the startup disk full error. It is because pre-installed programs can already take a significant portion of disk space and over time, different kinds of files will gradually fill the remaining space. Sooner or later, the user might receive this message:

Your disk is almost full. Save space by optimizing storage.

Sure, you can simply ignore it — just click Close and go on with your merry life. However, ignoring it over and over again will not solve the problem. You will eventually get another form of a pop-up that reads:

Your startup disk is almost full. To make more space available on your startup disk, delete some files.

Aside from this window popping up in the most inopportune moment, such as when you’re backing up your iPhone or saving a document that you have been working on for hours already, the issue can easily escalate. Eventually, you will notice your Mac starting to run slow, which defeats the purpose of owning a fast and reliable Mac in the first place.

For those who don’t know, it’s important to note that you should have at least 15% of free startup disk space for a Mac computer to run properly. So, if you keep on ignoring the friendly reminder to optimize your storage, your Mac will not thank you for it.

What is the Startup Disk?

By default, the startup disk is what’s known as the Macintosh HD. It is the partition in Mac’s hard disk where the Mac OS itself is installed. It is also where most of your files and apps are probably stored. Essentially, the startup disk is where the Mac OS will boot from, so it needs enough space in order to do its job. Once it begins to get filled, it will try to warn you before you experience the eventual slow-down.

The First Step: Knowing What’s Eating Up Your Startup Disk Space

Basically, fixing the startup disk full error requires freeing up disk space. But before you can do that, you first need to know what’s filling up space, so you’d know what you need to get rid of. Thankfully, this can be easily done.

• First, open the Apple menu.
• Next, go to About This Mac.
• Then, choose the Storage If you have an older version of OS X, you may need to click on More Info before you can access the Storage tab.

In this tab, you will see how much of the disk is occupied by certain types of files, which are:

• iOS Files
• Apps
• Documents
• Photos
• Movies
• Audios
• Backups
• Other

Once you know which ones take up most of the space in your disk, you will know where to start the purge.

How to Free Up Storage Space on a Mac

There are several ways on how to free up space on Mac and ultimately solve the startup disk full error. Luckily for you, almost all of these can be done easily.

1. Empty the trash.

This may sound elementary, but many of us forget about “taking out the trash” from our computers. When we delete files, they will go to the Trash, which serves as a holding area that you can go to in case you realize you need to recover what you deleted. However, the files in the Trash still occupy space, so you basically just moved the files to another folder. It is recommended to empty the Trash at least once a week. To do this:

• Right-click on the Trash in the dock panel.
• Select Empty Trash.

You can also open the Trash and click the Empty button found at the top right corner.

2. Clear cache.

A cache file is a temporary data file created by browsers, apps, and other programs. Even if you remove or stop using an application, the cache files remain in the Cache folder and when not checked, may take up a lot of space — we’re talking about tens of gigabytes here. So, it’s recommended that you clear the cache every once in a while. The Cache folders are inside the Library. You need to look for two types of these folders:

• /Library/Caches – This is where temporary files are stored. These files don’t usually take up too much space.
• ~/Library/Caches – This is where junk files created when you run apps go.

3. Delete logs.

While in the Library folder, you may also want to check the Log files, another type of temporary files. They can be found in the Logs folder. But before you delete any of them, make sure that you no longer need them.

4. Remove language resources.

You are probably unaware that your Mac has 26 pre-installed dictionaries, which can be considered the most underrated space eaters. If you don’t need German, Russian, or Dutch translations, for instance, you’d want to consider deleting them along with other localisations. These can be found in the following directory:

Macintosh HD -> Users -> Your User -> Library -> Dictionaries

5. Delete old iOS backups.

If it has become your habit to sync your other Apple devices with iTunes, it is possible that there are dozens of backups and they tend to take up a lot of space. To delete old backups, go to:

Library -> Application Support -> MobileSync -> Backup folder

Select old, outdated backups, then simply move them to the Trash.

6. Delete unnecessary documents, photos, and other files.

You need to take a look at your Downloads, Documents, Pictures, Music, and Movies folders and decide which files you no longer need. Next, organize the files that will be left behind. You might also want to consider moving them to an external disk or taking advantage of the iCloud storage.

7. Uninstall unused applications.

Applications are among the primary space takers, so it’s just logical to remove any that you haven’t used in a while and have no plans of using again. You need to remove them properly, though. Dragging and dropping them in the Trash won’t be enough. You also need to remove the cache and service files, which are found in the Library folder.

8. Take out the trash again.

Once you have deleted the files and folders mentioned above, they will naturally end up in the Trash, so you will need to empty it again.

9. Use an automated Mac cleaner.

Probably one of the easiest and fastest ways to clean up your Mac to free up space is to utilize an automated cleaner such as Outbyte MacRepair. Automated mac cleaners are designed to clean up your disk from time to time, checking for unnecessary and outdated junk, caches, files, programs, backups, language packs, and logs, among others. They even take care of emptying the Trash for you. These programs also recommend ways to better optimize your Mac. Tools such as Outbyte MacRepair offer a long-term solution to issues known to Mac, helping you maximize its potential as a computing beast.

A full startup disk is something that every Mac user will experience. This problem used to be known as “Startup disk full” notification. However, on newer macOS versions this message has been changed to “Your disk is almost full.”

But luckily, it’s a problem that has many solutions. And in this article, we’ll go over:

• What is startup disk full?
• What's causing 'Your disk is almost full' alert?
• How to fix startup disk full?
• How to prevent 'Your disk is almost full' problem?

However, we also understand that some people are short on time and just want to fix startup disk full. So, if you’re not really interested in what it is and why it happens, just skip the next two sections and head to “How to Clean Your Startup Disk”.

Or, even better, if you’re looking how to clear space on Mac, we’d highly recommend a utility called CleanMyMac X. It'll help you clean up gigabytes of disk space in just minutes (you can download it here).

Note: if you’re running macOS Sierra (or higher), it has a built-in option of Optimized Storage that is supposed to solve the problem of the full hard drive by moving files into the cloud.

By clicking 'Manage' you can open the menu and see what Optimized storage offers. However, it moves junk and useless files to the cloud together with your files, and eventually, you end up paying for iCloud storage to store junk. So we still recommend getting CleanMyMac and actually dealing with extra files rather than simply moving them.

Now, with all that said, let’s get into what exactly “Your disk is almost full” means.

Understanding What “Your Disk is Almost Full” Means

What is a startup disk?

A startup disk, as taken from Apple Support article, is a volume or partition of a drive that contains a usable operating system. Still confused? Let’s break it down for you.

Your Mac hard drive consists of disks (or partitions). Each disk (or partition) has your Mac data on it, which consists of your operating system, applications, etc. Most Mac users have just one disk but power users may have two or more.

Let’s look at an example of a Mac with only one hard disk:

• Your Mac's hard drive is 500GB.
• It has one 'disk' on it, so all 500GB of storage is on that disk.
• The disk has an operating system (OS X El Capitan), and user data (apps, etc).
• And since you only have one disk, this is your startup disk: all 500GB.

A Mac with two disks will have the storage divided between them. The Mac drive with the OS on it is the startup disk while the other drive is just used for storage of files. It’s possible to have multiple startup disks, but most Macs will only have one.

Why your disk is almost full?

This is easy. It’s a lot like why is your fridge full? There is no more space! Your disk is almost full and this is very bad news for any drive. A hard disk should never get beyond 85% capacity (especially a startup disk) as you will experience slowness and errors the further you get above that mark.

If your startup disk is full and you get a message of warning from your Mac, this is a serious indication that you need to clear up storage immediately.

What to do when your disk is almost full?

So how do you fix your almost full startup disk? The same way you solve the problem of a packed fridge - you need to clear up storage, of course. To make more space on your startup disk you will need to:

1. Delete files from your Mac.
2. Move files to an external hard drive or cloud storage.
3. Or install a second internal hard drive on your Mac.

So, now that we know what a startup disk is, we need to talk about how to fix it. Let’s take a closer look at your disk space to see exactly what is causing your disk to be almost full.

What’s Causing 'Your Disk Is Almost Full' Alert?

Short version: Take a look under-the-hood of your Mac.

Before we can see what is taking up space on your startup disk, first we have to find it:

1. Hover on the Dock at the bottom of your screen and open Finder.
2. Click on “Finder” in the menu bar at the top of your screen.
3. Then select “Preferences…”
4. In the window that opens, checkmark the “Hard disks” checkbox.

After selecting this box, your desktop should now show the hard disks on your mac, in the form of icon(s), like this:

These are disks on your Mac that you can “startup”, this is because they have operating systems on them. If there is more than one of these hard disk icons that show up on your desktop, it means you’ve got multiple hard disks on your Mac. If you only have one, skip the down to “What is taking up all of my startup disk space?” section.

If you have more than one, continue with the next step:

Click on the Apple icon at the top left of your screen System Preferences > Startup Disk.
Here, again, you’ll find your hard disk(s); they’re probably named something like MainSSD or MainHD. It will also display “OS” and the version number of that OS. If you have more than one OS drive, your startup disk should be the one with the latest version of macOS running on it, but we’re going to make sure of that in the next step.

I only have one and it looks like this:

To make 100% sure that you know what drive is your startup disk, follow these steps:

1. Click on the Apple Icon in the menu at the top-left of your screen.
2. Select “About This Mac.”
3. Under macOS, you’ll find a version number. Mine is 10.15.1, like so:

See how my version number in the “About This Mac” window matches the number in my Startup Disk section? Yep — That’s my startup disk. Found yours? Good.

What is taking up all of my startup disk space?

Now that we’ve identified our startup disk, let’s take a closer look at how to clear up space on Mac:

1. Click the Apple Icon in the menu at the top-left corner of your screen.
2. Choose “About This Mac.”
3. Click Storage.
   Note: If you are running an older version of OS X you may have to first click “More Info…” and then “Storage”.

Take a look at my hard drive disk:

I’ve got 500GB of storage, and about 275GB of it is free.

So, how big is your hard disk? How much free space do you have (if any — *gulp*)? And what’s taking up the most space? It is important to consider drive capacity and data storage needs for future storage plans — we’re not just here to fix the problem, for now, we’re going to make sure you never have this problem in the future as well.

Now that we have the knowledge, it’s time to take action and fix your Mac’s “Startup Disk Full” problem.

Let’s go over 11 things you can do to help fix 'your disk is almost full.' These should also give you other ideas as to how else to fix it — You know your Mac better than we do!

Free Up Space On Macbook Yosemite

1. Clear system storage on Mac

System storage cleanup sounds like a serious undertaking. But, technically, it boils down to just one thing: having the courage to scrap the old files.

1. Search for large ZIP/RAR archives in Downloads
2. Open your Desktop (Command + F3) and delete screenshots
3. In Applications, sort your apps by size. Delete the largest ones
4. Get rid of system junk files with a free version of CleanMyMac X
5. Restart your Mac to free up RAM.

2. Clean up cache files on your Mac

Cache files are files that help your Mac run programs a bit more smoothly. Think of them like blueprints for a house: your Mac has the blueprints for how a program is supposed to load/run/look, so it loads it faster; without them, it’d be like building it from scratch. However, over time, these caches can start to take up some serious space. Periodically, removing them can help clear storage. And don’t worry, your Mac will create fresh, new ones after you restart your Mac. To remove caches:

1. Open a Finder window and select Go in the menu bar.
2. Click on “Go to Folder…”
3. Type in ~/Library/Caches
   Delete the files/folders that are taking up the most space.
4. Now click on “Go to Folder…”
5. Type in /Library/Caches (simply lose the ~ symbol)
   And, again, delete the folders that take up the most space.

Deleting cache files is generally safe for your Mac. And once you delete them, the applications and processes you run on your Mac will generate fresh, new ones. But, when deleting, worry more about removing them based on size rather than just removing all of them.

Also, you can check the /System/Library/Caches folder as well, but it might be better not to touch this folder without knowing what the items are. A utility that correctly cleans up these files (and pretty much everything else on this list) is, you guessed it, CleanMyMac X. It cleans up even your system caches with just a few clicks.

Oh, and once you’re done with this list, restart your Mac so it can create these new cache files.

Read more: How to Clear Cache on a Mac?

3. Get rid of localization files

Localization files are also known as “language packs.” Lots of apps come with other languages that you probably don’t need. To clear up space on your Mac, delete the ones you don’t need:

1. Open a Finder window.
2. Go to Applications.
3. Ctrl+click on an application.
4. Select “Show Package Contents.”

From here, go to Contents > Resources and look for files ending in .lproj. These are the languages your app has just in case you want to use it in another language, like Spanish (es.lproj). Drag the ones you’ll never use to the Trash.

Again, a safer alternative to this would be to use CleanMyMac X. It gets rid of all of them with a click. No digging through application folders, just a cleaner Mac.

Read more: How to Delete Language Files from macOS?

4. Delete duplicate files

Even if you have the most organized Mac on a planet, duplicates happen one way or another. It can be a file you’ve mistakenly downloaded twice or a mail attachment you’ve opened several times. Regardless of how they appeared, those files sit on your Mac and gobble up storage.

But finding and deleting them is a time-consuming process if you do it one by one. So here’s what you can do to save up time:

1. Open the Finder app on your Mac
2. Move cursor over File and click New Smart Folder
3. Click the “+” button in the upper right corner and choose the type of files you want to see
4. Now sort them by name to quickly spot duplicates.

Remember to pay attention to the date of creation to make sure you keep the true original, not the copy.

While this is the best way to remove duplicates manually, it takes lots of your time and dedication. It’d be much easier to leave this to Gemini 2: The Duplicate Finder.

This app quickly scans your Mac for duplicate and similar files and allows you to delete them within minutes. It keeps your originals safe and helps you easily retrieve files deleted by accident.

5. Remove old iOS backups

Backups can tend to take up a lot of space. You can find and remove them by:

1. Launching a Finder window.
2. Clicking “Go” in the menu bar.
3. Selecting “Go to Folder…”
4. Then, type in ~/Library/Application Support/MobileSync/Backup/

Get rid of all the old, outdated backups your Mac has been storing for a bit more extra space.

Macbook Air Free Up Space

6. Remove iOS software updates

You can find all the unnecessary data for your devices by:

1. Opening Finder.
2. Selecting “Go” in the menu bar.
3. Clicking on “Go to Folder…”
4. And entering for iPad ~/Library/iTunes/iPad Software Updates
   or entering for iPhone ~/Library/iTunes/iPhone Software Updates

Delete downloaded files for any of the devices that you are not using anymore, or ones which software just already updated. Remember that after any of your devices have been updated, you don’t need those files.

Read more: How to Delete iOS Software Updates from Mac?

7. Remove unnecessary applications

This isn’t often overlooked, but definitely under-appreciated. Removing old, unused applications is a great way to get some extra space on your startup disk. Go through your applications folder and get rid of all the apps you rarely use. But make sure you remove them correctly, don’t just drag them to the Trash. If you do, you’ll leave behind tons of leftover parts and pieces, and we’re trying to get back startup disk space — It’ll kinda defeat the purpose, no?

This is another place we’d suggest using CleanMyMac X. To completely remove any application, just launch CleanMyMac X, click Uninstaller, select your application, and then click Uninstall. You won’t have to search all over for development junk that’s left behind when Trash’ing an application. It’s incredibly easy and saves you tons of time.

8. Clean up your photo library

Photos, photos, photos. Talk about tons of space! First and foremost, select only what you can get rid of, like image copies and maybe some photos that were mistakenly taken. You know, ones of the ground or something?

Ok, once your own files are taken care of, it’s time to get rid of the files your system created. In Photos for Mac, it’s cache files. In iPhoto, it’s service copies. Both are a pain to find, but here’s how you can get rid of them.

Photos cache includes iCloud local copies (created when you view pics from your iCloud photo library on a Mac), Faces cache (generated when you use Faces), and other app-related caches. You’d be surprised how much all that takes up if you regularly use Photos. For OS versions prior to macOS Sierra, here’s the path to locate the cache:

1. Open Finder and navigate to your Photos library (normally, it’s in the Pictures folder).
2. Ctrl+click your Photos library, and select “Show Package Contents.”
3. Open resources, and then modelresource.

You should now see a lot more folders in your Finder window. Photos cache sits in these folders, but the tricky thing is that it’s really hard to say what is safe to remove and what isn’t. Deleting the wrong file can compromise the performance of Photos, which is why we highly suggest you use CleanMyMac X to clear the cache and system junk. It only removes files that are safe to delete, never a critical file or important image.

You can download CleanMyMac X for free and see how it works, it’s so much safer than cleaning up system junk manually.

9. Clean up your Downloads, Movies, and Music folders

Have a closer look at these three folders. You’d be surprised at how many downloads can accumulate when you aren’t paying attention. Clean out anything you don’t need (or don’t know) and organize the rest. It’ll take a load off your mind to know that there’s nothing excess there.

The Movies folder can be a pain, not because you’re searching through tons of files, but it can be difficult to choose what to delete. Personally, I never want to get rid of Top Gun. It’s amazing. I watched it 3 times in a row last weekend. But alas, sometimes you need to make sacrifices for the health of your Mac. Though, what you can do with movies you want to keep is to archive them. So, archive what you wish to keep and remove the rest.

How to archive/compress a file

Archiving a file doesn’t mean to store deeper into the abyss of your Mac — but to turn the file into something smaller, into a compressed file (like .zip or .tar). By archiving a file, you shave off some memory. Archiving is essential for things you want to keep on your Mac, but don’t often use, and helps you clear up some space. And that’s what this is all about right? We’re essentially doing the hokey-pokey on your Mac. To archive a file, just:

1. Ctrl+click the file you want to compress (recommended for movie files).
2. Select, “Compress .”

The last place to sweep through is the Music folder. Find and remove duplicate music files first, and then clean up all the songs you downloaded on a weird Sunday afternoon cleaning the house.

10. Clean your Desktop

“Clean my desktop… but why?” Because some people’s desktops are hard to look at, that’s why. Organize your desktop and get rid of the stuff you just don’t need on there. It looks better and helps your Mac act a bit faster (I don’t know the rocket science behind this one, but it feels too good to be false). Your Mac doesn’t waste time loading all those icons and junk, just… Just clean it, please.

11. Empty out the Trash (No, we’re not joking…)

Seriously: It may sound incredibly basic, but it could clear a surprising amount of storage. I forget to do it all the time. The thing is, that when you delete something, your Mac doesn’t remove it — it just moves it to the Trash. Plus, you’ve probably deleted way more than you realize, and all that could be sitting in the Trash, wasting space. So get rid of all that junk by emptying the Trash:

1. Ctrl+click your Trash in the Dock.
2. Select “Empty Trash.”
3. And click “Empty Trash.”

And, the easiest step is done.

A few more tips to clear storage on Mac

1. Manage your Optimized Storage

This option comes with your operating system starting macOS Sierra. Go to the Apple menu > About this Mac > Storage

Now, click on Manage to reveal the space-saving options:

2. Erase your Junk Mail

Open your Mail app, and click Mailbox in the upper menu. Here you can erase spam and already deleted items.

3. Delete system junk with CleanMyMac X
Again, this is an incredible utility when it comes to cleaning your startup disk. And this app is notarized by Apple, meaning it's safe.

To avoid the annoying “your disk is almost full” error, download the free edition of CleanMyMac X.
Once you've installed the app, click on the System Junk tab. It will clean up caches, logs, language packs, binaries, duplicate photos, outdated backups, Trashes, and more.

Full Startup Disk Prevention

We’ve cleaned up a few things on your Mac, and hopefully, it’s given you more ideas as to what else you can clean. But, let’s take a look at how much space you saved from cleaning the list above. Remember how we checked your Mac’s free space? Open that window again and see how much space you’ve cleared up:

1. Click the Apple Icon in the menu at the top-left corner of your screen.
2. Choose “About This Mac.”
3. Click Storage.
   Note - If you are running an older version of OS X you may have to first click “More Info…” and then “Storage”.

You’ve probably got a bit more space, and you’ll want to keep it that way. The only way to prevent a “your disk is almost full” is by keeping your Mac clean. We’d recommend a complete cleaning every 2–3 weeks.

Say goodbye to the 'Your startup disk is almost full” message.

Free Up Space On Macbook El Capitan

So, we’ve now covered everything that we wanted to share with you. Hopefully, this has helped you fix that full startup disk problem. Your startup disk should now be quite a bit lighter (we hope). Oh, and if you liked this article, get social with it to help others in need. And if you really liked this article, subscribe to our email list — we’ve got more guides on the way. And we’ve also got a utility that’ll help you out a ton in the long run: CleanMyMac X. It helps you clean your entire Mac with just the click of a button. It’s incredibly easy to use and works like a charm.

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