Back in the days of hard drives we all had tons of space on our Macs, but in these days of SSD or flash drives we’re much more limited, with some Macs hampered by just 128GB storage.

If you want your Mac to run smoothly you need to make sure that you have something like 10 percent of your storage free at all times, so if you are running out of space it can really hamper your computing.

We recently ended up with less than 5GB space left on our 128GB MacBook Pro and had to spend some time spring cleaning our system to claim back some space. Luckily for us, Apple made the process considerably easier when it launched macOS Sierra in 2016. We will take your through the steps we went through in the article below. If you have not yet updated to Sierra (perhaps you need to make some space in order to do so) we have all the steps you need to follow further down in this article.

Skip down to see the best software for clearing up your Mac here.

How to manage storage using macOS Sierra

In macOS Sierra Apple introduced a new Optimized Storage feature that helps you delete old files or move things you don’t need on your Mac over to the cloud.

Should you be running out of storage, as we were, you will keep seeing alerts on your Mac which will provide a link to your storage preferences. To access this same pane you need to click on the Apple logo in the top left of your screen and choose About This Mac.

Next click on the Storage tab. This will show you how much storage you have available and how it is used. You will see a bar which indicates how much space is given to Photos, System, Apps, Mail, and finally ‘Purgeable’.

In our case we have more than 92GB of photos on our 121GB drive, and 738MB of purgeable stuff.

Click on the Manage button. This will open another pane in which you are given four options: Store in iCloud, Optimize Storage, Empty Trash Automatically, and Reduce Clutter. You will also see a number of tabs on the left hand side of the window for Applications, Documents, GarageBand, iCloud Drive, Mail, Photos and Trash.

On a more populated Mac you will also see tabs for iOS Files - which is helpful as if you back up your iPhone or iPad to your Mac (or you have in the past) you may find loads of iOS Apps lucking - none of which you need to keep as you can easily download any you have previously paid for. iOS apps can take up a lot of space so you could quickly win back some storage space this way. You’ll also see iTunes here which will be populated with all the music you store on your Mac - which could take up tons of GB if you don't subscribe to Apple Music or iTunes Match to keep your music in the cloud.  

You can click on any of these options on the left to see more information about those files types. Click back on the Recommendations tab at the top of the list on the left and you’ll be taken back to the options.

We will come back to Store in iCloud...

Optimise Storage automatically

This option will delete TV shows or films that you’ve watched, it will also remove email attachments. You needn't be afraid of losing either of these things because the emails will still be stored on the iCloud server anyway, and the shows you had purchased from iTunes can always be downloaded again for free. All you need to do is click on Optimise and the Mac will do the work for you.

 Empty Trash Automatically

Chose this option and macOS Sierra will empty files out of your Trash after they have been there for 30 days.  Click Turn On… and you will see an alert asking if you are sure that you want to erase Trash automatically. It should be pretty safe as 30 days is a long time to realise you didn’t mean to delete something, so we recommend you click Turn On.

Reduce Clutter

Reduce Clutter will review the content of your Mac and delete older documents. Click on Review Files and you will be taken to a pane that shows Large Files, Downloads and a File Browser. We don’t have many files on our MacBook Pro because we store most of them on iCloud, but if we had files on the Mac we’d be able to see the largest files on our Mac, including when we accessed them last and their size. Click on the magnifying glass icon to see a preview of the file, and click on the x to delete it.

Store in iCloud

Store in iCloud is a little less straightforward. It gives you the option of storing files in iCloud, for a price. Apple does give users 5GB of iCloud storage for free, but that’s not really going to help you here. The prices for iCloud storage are as follows:

  • 5GB free
  • 50GB £0.79 a month
  • 200GB £2.49 a month
  • 1TB £6.99 a month
  • 2TB £19.99 a month

Click on Store in iCloud and a window pops up asking if you want to store photos and videos in iCloud. Given that our Photo library is 96GB it seems like it might be a good idea to pay for the 200GB of space Apple is offering. Click on Store in iCloud and enter your password in iCloud in System Preferences.

Storing photos and videos in iCloud doesn’t mean that they will disappear from your Mac, however.  iCloud Photo Library mirrors the photo libraries on your devices so that rather than seeing the photos stored in the library on your device, you will see all the photos stored on all your devices on each device.

The problem here is that when you turn on iCloud Photo Library you could actually end up downloading photos from your other devices to your Mac, so it’s not necessarily going to save you any space. In fact it could do the opposite - in fact, it’s the reason why our photo library grew so quickly! For this reason when/if you set up iCloud Photo Library we recommend you open iPhoto and go to Preferences > Optimise Mac Storage, before you download or you could be downloading originals.

If that’s what happened to you it may look like a good idea to disable iCloud Photo Library. If you disconnect from iCloud Photo Library and then delete the photos on your Mac, they should still be available in the cloud.

You will be able to download the optimised versions again should you wish to connect to iCloud Photo Library again in the future. However, if you disconnect from iCloud Photo Library any photos you upload to your Mac in the future will not appear on your other devices. It will be a separate photo library until you decide to link it up again.

We tested this on our work Mac. While connected to iCloud Photo Library we had 56.62GB of photos and videos, while there is 103GB of photos in iCloud (102.98GB to be exact). When we turned off iCloud Photo Library we were warned that any photos and videos that we hadn’t fully downloaded to this Mac would be removed, although they would still be available on other devices using iCloud.

Downloading them would theoretically fill up that Mac too, so we chose to Delete from Mac. The next warning was that 9876 low-resolution photos and videos would be removed from the Mac, but that the full-resolution versions would remain in iCloud.

We chose to Delete from Mac. As far as we could see the photos didn’t magically disappear from our Mac, however, although the photo storage went down to 54.99GB. After manually deleting a few more photos it declined further to 51.22GB. The iCloud photo storage remained at 103GB so we are confident that we hadn’t deleted any photos from iCloud.

We still think the best solution for a big photo library is to invest in a separate hard drive and transfer your photo library to that. We have a tutorial about how to do that here: How to move an Apple Photos for OS X library to an external drive.

To summarise, this is how to move your Photo library to an external drive:

  1. Quit Photos
  2. Copy your Photos Library to an external drive. (To save having to delete them again after, press the Command key when you drag the files over so that they are moved, with the original files automatically deleted, rather than copied).
  3. Once the files have finished copying, hold down the Option/Alt key while starting up Photos.
  4. In Photos select Photos > Preferences and in General choose Use as System Photo Library.
  5. If you have iCloud Photo Library enabled, the Mac may get busy as it works out which photos reside in iCloud, but if should eventually complete without requiring a massive data transfer.

Even if you haven't installed macOS Sierra there are still some tricks you can use to claim back some hard drive space - some of which may still prove useful post Sierra.

Remove photos to free up hard drive space

The first thing you should do when you decide to free up space is pick the low-hanging fruit, i.e. those files which occupy tens of gigabytes of disk space on their own. One good place to start is your photo library.

If you are anything like us you probably take a dozen photos for each photo you actually choose to put in an album or share on Facebook. Once in a while it's worth taking some time to delete these extra unneeded shots. If you haven't done this from time to time spending some time now is probaby a good idea, even if you intend to just copy over your entire Photo library to an external drive or to start using iCloud Photo Library (both of which are covered in detail above).

Here's another tip: If you've been a Mac user for some time and at one point migrated to the Photos app from iPhoto or Aperture (or both applications), you may find that there are files created by Aperture and iPhoto still lurking on your Mac. Both those apps stored their libraries in a single file, located in Pictures in your user directory.

When you migrated to Photos from Aperture or iPhoto, the old library files remain in your Pictures folder, meaning you now have a Photos library and an Aperture or iPhoto library. If you never plan to use Aperture or iPhoto again, you can get rid of their libraries, but we'd recommend archiving them on an external hard drive just in case (Note, there can be some confusion about your photo library in Photos and iPhoto - the apps are accessing the same images, so your whole library isn't duplicated, but there are associated files that you no longer need).

We had a 6GB iPhoto file on our Mac. Right click on it to "Show package contents" and remove all bar the Masters file.

Crop iTunes to recover storage space on your Mac

Your iTunes library is another candidate for re-claiming disk space. You have a number of options here. You can copy the whole thing from your Music directory to an external hard drive and point iTunes to it from its Preferences. That's great if your Mac is a desktop model, but not ideal if it's a notebook.

You could use a NAS box instead of an external hard drive in that instance, so that you can access your music whenever you're connected to your local network.

A third option is to pay £21.99/year to subscribe to iTunes Match. Here's how to set up iTunes Match.

Once you've set it up, iTunes Match allows you to access all the music in your iTunes Library on Apple's servers, meaning you don't have to have it stored locally at all. You'll need to be connected to the internet in order to play music, but other than that, it's just like using iTunes with locally stored music.

And, as a bonus, if you decide at a later date that you want to download your music from iTunes Match, you get 256-bit AAC files which are probably of better quality than the ones you had stored on your Mac.

The final option here is to subscribe to Apple Music, Apple's service that for £9.99 a month gives you access to its whole music library, so assuming that all the music you enjoy is on iTunes you can delete all your music from your Mac and just stream the music from Apple Music instead.

If at a later date you decide not to subscribe anymore, you will always be able to download for free any tracks you bought from the iTunes Music Store before you took out the subscription, but note that unless you have iTunes Match you won't be able to download tracks that you uploaded to your iTunes library yourself, so don't throw out those CDs just yet.

Remove files from your Downloads folder

Your Downloads folder also probably houses large files you know longer need. If you download large PDFs, images, or disk image files and don't prune Downloads regularly, it's probably full of stuff you don't need. Start with disk images. If you've installed their contents, you won't need them anymore. If they contain apps, you should always install the latest version anyway.

Find out what apps are hogging space on your Mac

Once you've dealt with the obvious culprits, it's time to go deeper and find the other disk hogs. There are several apps that will show you which files are taking up big chunks of disk space, or allow you to order files in the Finder based on their size.

GrandPerspective (free) and DaisyDisk (£9.99, buy it here) give good visual indications while OmniDiskSweeper (free) uses the standard hierarchical file window to show the sizes of every file and folder. Other apps such as CleanMyMac 2 (£34.95) show disk usage as part of their cleanup features.

How to see what files are taking up the most space on a Mac without buying an app

You can also do it easily without an app. Open a new Finder window and navigate to your Home folder, or press Shift-Cmd-H from the Finder. Press Cmd-F to open a new Find window and in the left hand dropdown menu at the top of the window, choose Other. From the window that opens next, scroll down until you see File Size, and check the box next to it.

You have now selected that as the attribute for a search. Select 'greater than' in the next dropdown menu, and change the file size units to MB. Now type in a file size, say 100, to display all the files in your Home folder that are bigger than 100MB. You can now choose which files to delete or archive on an external disk, and free up disk space quickly.

Empty the trash to recover space on your Mac

Empty the Trash frequently. If there are any stubborn files that won’t disappear, the easiest solution is to use Trash It! (free), a useful one-trick pony.

Delete attachments from Mail to save space on your Mac

How about your Mail attachments folder? Think about how many emails you receive with large attachments. What happens to these? Within the main Mail folder (~/Library/Mail), attachments for incoming mail are stored in the inbox folder.

To make sure those from deleted emails are removed, go to “Remove unedited downloads” in Mail’s preferences and select “After Message is Deleted”. The current version of Mail also stores attachments in ~/Library/Containers/com.apple.mail/Data/Mail Downloads. As long as you don’t need them these can also be deleted, often saving you many hundreds of MB.

Remove duplicate files from your Mac

Identifying and dumping duplicate files is another good way of freeing up disk space. Gemini costs £15.95 on the Mac App Store (in the US you can buy it on the Mac Store for $19.99) and allows you to scan your Mac for duplicate files so you can dump one copy.

How much of your precious hard drive space is being taken up by duplicate files? While hard drives may be getting bigger and cheaper, Apple’s direction is that of smaller, faster SSD drives. The problem is that these have smaller capacities so a higher level of filing discipline is essential.

There are a number of reasons why you end up with so many dupe files. When you add songs to iTunes, if you have ‘Copy files to iTunes Media folder when adding to library’ checked in the preferences, you keep the original. Instant duplication. A couple of thousand high quality songs and that’s anything up to 10GB hard drive space wasted. And that doesn’t include dupes within iTunes.

If you use Apple Mail, remember that all attachments reside in Mail’s own download folder. This can be another source of duplication.

More generic apps use various strategies and criteria to find duplicates and give you control over which ones to get rid of. Have a look at Tidy Up ($29.99) or Singlemizer ($19.99, buy it from the Mac App Store here).

Quit apps that are running in the background to free up space

Quitting apps that have been open for several days or more, or even restarting your Mac completely on a regular basis will also help free up disk space. Applications create temporary files to store data and the longer they run without quitting, the bigger those files become. When you quit the app, the cache files are deleted and the disk space returned.

Get rid of unwanted Mac apps to save space, delete associated support files

It’s amazing how many apps you can acquire over a short period of time let alone over the many years most of us have been using a Mac. Most Mac OS X apps are bundles. The application is usually a special folder that looks like a single, double-clickable file and contains almost all the files needed to run the app. Trashing the app is easy; getting rid of all the support files isn’t. There are preferences (plist) and application support files and these can exist in a number of places on your Mac. These files along with the app itself may be wasting many gigabytes of your hard drive space.

Some major apps include an uninstaller. For example, you’ll find one of these in the Additional Tools folder of Microsoft Office. Sometimes an app’s installer doubles as an uninstaller. But the lack of a dedicated uninstaller in Mac OS X is a serious omission.

Fortunately there are a number of third party options. AppCleaner (free, download from the Mac App Store here), AppDelete ($7.99, there's a Lite version on the Mac App Store here for £2.99) and AppZapper ($12.95) all do the same job – but the fact that they each find different files to remove shows how complicated a process uninstalling can be!

Remove extra languages you don't need

Mac OS X supports a range of languages, being localised for over 25 languages all of which are included automatically during installation. Go to System Preferences > Language & Region, here languages can be put into preferred order making it easy to switch between them.

Many major applications support multiple languages too, using the order from Language & Text to select one if the app doesn’t support your main language. The problem is that if you only want to use one or two languages, Mac OS X and many of your apps are bloated with all the others.

If you want to delete extra language files that you know you won't be needing, go to the Resources folder and look for folders ending in .lproj. Each of those folders will include a language file. You should be able to trash these folders withouth any problems.

Remove unwanted code to save disk space

Getting rid of unwanted code is another disk-saving exercise. Universal Binaries host both PowerPC and Intel architectures yet since Lion, the former is not supported.

Monolingual (donation requested) lets you remove specific architectures from Mac OS X along with specific languages. While it can claw back huge swathes of hard drive space, unless you’re careful with the preferences it can also render your Mac unbootable so use with extreme care.

Use Cloud storage space to supplement the capacity of your Mac's hard drive

Cloud storage services are great for making files available remotely, but they can also take up space on your Mac. Both Dropbox and OneDrive for example, sync everything you store in them with your Mac by default – assuming you've installed the Dropbox/ OneDrive app.

If you only have the default 2GB storage available for free from Dropbox, that's not too much of a problem. But Microsoft gives Office 365 subscribers 1TB of space free, so if you use that to store lots of files, you could find yourself running out of disk space very quickly. The same is true if you pay for more space on Dropbox.

In both cases, however, you can choose to sync only files and folders you specify. In Dropbox, click on the menu bar item, then click the cog and then Preferences. Click the Account tab, then click Change Settings. Now untick the files and folders you don't want to sync with your Mac. In OneDrive, click the menu bar item, then Preferences. Click Choose Folders, then Choose Folders, then Choose Folders to sync. Untick folders, or click the expand arrow to access individual files and untick those.

A alternative would be to sign up for more iCloud storage, as we mentioned earlier, 200GB of iCloud storage costs £2.49 a month, £6.99 a month for 1TB, or £13.99 for 2TB, there's also a 50GB option for 79p a month... And it's easy to access from any of your Apple devices.

You might be thinking I need the space, but I don't want to delete anything!

I really need to keep everything!

If you really are the proverbial data squirrel, here are a few simple suggestions:

• Archive any files you are unlikely to need regularly. Control-click on a folder and select the compress option. The space saved will vary according to the type of file being archived: JPEGs and DMGs, for instance, are unlikely to compress very much. Once created, archives can either remain on your Mac or be saved to an external drive.

• Use an external drive for data files. This would be especially useful for design, audio or video files.

• Migrate your iTunes Music folder to an external drive and then relink to this within iTunes. This is quite possibly the single largest folder on your Mac: mine is a disk-busting 25GB.

Finally, if you do take the decision to delete files or folders, always back them up first. You never know…

Read more like this: 15 apps you should install on your Mac | 10 really useful built-in Mac apps | How to clear Safari cache, history and cookies.