No space left on device on Mac: Why it happens and how to fix it

Ever found yourself staring at the no space left on device Mac error when browsing on Safari or busily working away? It’s got to be one of the most frustrating scenarios out there. It basically means either one of two things. You have a full-on genuine storage shortage, or it’s a known macOS Safari glitch, where this error message triggers even when you’ve got loads of free space. I’ll help you figure out what’s causing yours.

What does the no space left on device Mac error really mean?

Your macOS is telling you that its disk or a current process simply can’t write data because it believes there isn’t enough room. If you want to get super technical, it points to the POSIX error ENOSPC, often shown as NSPOSIXErrorDomain:28.

So, as I mentioned in the intro, there are essentially two causes.

• Safari, known macOS bug

If you have available disk space but you keep getting this pop-up error when you’re using Safari, the forums are rife with threads on a known issue, which is actually caused by Safari’s Hide IP address from trackers privacy feature.

• Actual full disk

You’ll also get this error when the startup disk genuinely has little or no free space left.

Check which issue is causing your message by going to Apple menu > System Settings > General > Storage.

System Data includes caches, logs, temporary files, app support data, and local snapshots. While the macOS category is the operating system itself.

Visible free space is also confusing because purgeable space and Time Machine local snapshots don’t act like normal empty storage.

How to fix the Safari no space left on device error

So, if your system data Mac storage wasn’t an issue, then you’ve got the Safari glitch; here’s how to fix it.

Step one: Disable hide IP address from trackers

So in Safari, go to Settings > Privacy > uncheck Hide IP address from trackers.

Step two: Clear Safari cache and website data

Now, you should clear the cache in Safari > Settings > Privacy > Manage Website Data > Remove All.

You can also go a step further and go to the main Safari menu bar > Develop menu > Empty Caches.

Step three: Update macOS and Safari

This glitch has been patched. You should check you’re running the latest macOS version. Go to System Settings > General > Software Update.

Step four: Check third-party tools

Tools like Little Snitch, Radio Silence, or VPNs can cause conflicts with Safari. Disable them, test if you’re still getting the error. Finally, restart your Mac to resolve any last-minute issues.

How to free up disk space on Mac

Got a genuine storage issue, here’s what I would do.

Step one: Check what is using your storage

In your main Apple Menu > System Settings > General > Storage, identify the biggest storage categories.

Step two: Empty trash Mac

Trash stays in your Trash taking up space until you actually empty it.

Step three: Delete large and old files

Go to your Downloads folder, and sort items by size. Then, you can delete the stuff you forgot about, that's consuming storage. You can also use Finder for this, sorting by size to find hidden files and documents.

Step four: Clear system junk and caches

Your macOS hoards caches, useless system logs, and even broken files, which, as you may have guessed, all take up vital space. If you go to Finder, press Go > Go to Folder and type in ~/Library/Caches, you can clean these manually, but I’ve got to be honest, it’s a bit tedious and risky if you don’t know what you’re doing. The Cleanup feature from CleanMyMac is a safer bet for many users, because it can do this all in one click, and most importantly, safely, often removing up to 20 GB of hidden junk. And you can test it for 7 days free — get your free trial here.

Step five: Remove unused apps and leftover files

When it comes to knowing how to free up space on a Mac, removing apps is an important step, but dragging them to your Trash isn’t enough; it leaves behind leftovers that sit there taking up space. Use the Applications feature from CleanMyMac — this completely removes apps and all hidden support files.

Step six: Manage your Mail attachments and local backups

You can delete old iOS backups in System Settings > General > Storage > iOS Files.

Mail attachments is another good thing to look at, because they can consume so much space unknowingly, spend some time looking through your old emails.

Step seven: Time Machine local snapshots

Time Machine local snapshots are normally cleared automatically as space is needed.

System data Mac storage: How to prevent future issues

Always keep your Mac up to date; this means you’ll benefit from new patches that fix bugs. Keep at least 15 - 20 % of your disk space free at all times. At least once a month, check your storage levels and think about removing media to a cloud solution. Remember to regularly remove apps you don’t use or need.