MacOS 27 will solve System Data bloat???

You should aim to have 15-20% of your total internal storage as free space (~20-25 GB as an absolute minimum). If you do not have enough free space on your Mac’s internal storage, then here are some steps to take to safely free up space:

Free up storage space on Mac - Apple Support

Optimize storage space on your Mac - Apple Support

How to free up ‘System Data’ and other st… - Apple Community

"System Data" comprises your data, but they are typically hidden files that Spotlight cannot assign to a specific category like Documents or Applications. Examples include Outlook attachments, iOS updates, Cloud storage caches, etc. Starting with macOS 27 Golden Gate, System Data also includes what macOS used to call ‘purgeable’ storage – system caches, Time Machine snapshots and some other data, though the user had no control over the purging. That means macOS 27 makes System Data bigger, not smaller.

Trying to manually clean out hidden files in System Data is likely to cause more problems than it solves, macOS hides those files for a good reason. Follow the steps in the linked articles above. 

On macOS 27, separate ‘purgeable’ space is no longer reported, and instead those data are now considered as used space. They are also now included in System Data, accounting for the apparent increase you would see. You won't lose space, macOS just categorizes things differently than on Tahoe.

More detail on this change in this User Tip:

System Data and Free Space Changes in Gol… - Apple Community

The best advice is to just ignore the System Data category. ‘System Data’ is merely a catch-all category for files that Spotlight cannot assign to specific categories like Applications, Documents, Photos, etc. In fact, what is now shown as System Data used to be reported as ‘Other’, Apple changed the label in macOS 12 Monterey. System Data probably sounds better, but Other was closer to reality. 

mhb wrote:

I have a big problem with System Data bloat. I have a 500 GB drive on a 2020 Macbook Air running the latest MacOS 26 version, and 220 GB is System Data. I've tried to get that down using the various tips provided online but nothing has worked, including starting up in Safe Mode, deleting cache and logs ...

That is because in many (not all) cases, "System Data" can be mostly your own files, that Apple doesn't have an easy way to categorize, as others have pointed out. You can figure this out if you obtain a utility like Stereograph or DaisyDisk (I have both, these each do require a small payment but it may be worth it if you have 220 GB (40% of your disk) and don't know what it is. Those utilities drill down and will find and identify everything on your drive.

By the way, your use of the term "Bloat" is interesting. In many cases, this "System Data" includes files that the user has created from the apps or software that they use.

I asked about this at the Apple Store last evening and was told that if I download MacOS 27 it will clear out the System Data bloat. Can anyone confirm that's the case? I know just updating within the current MacOS 26 keeps all that bloat. Is it different when downloading a whole new OS?

I don't believe that what you were told is correct.

I'm at the point where I'm wondering if I need to get a new computer and drag my files over and reset my preferences and start over (ugh), but if just updating to MacOS 27 will help, I'd rather wait on the new machine. Thanks.

Well, I don't think that will work if you drag back over all your files as that would simply bring all that "System Bloat" over to the new computer. It could become an expensive undertaking that does not help you in your use of disk space.

I have several Macs in use and "System Data" ranges from 40 GB to 100 GB on these Macs, which are on OS from Monterey to Tahoe. The MacOS itself on one of the Tahoe machines takes about 20 GB.

mhb wrote:

I've tried to get that down using the various tips provided online but nothing has worked, including starting up in Safe Mode, deleting cache and logs ...

Not surprising. The internet's not true. Deleting cache files and logs will have no impact other then slowing down your computer.

I asked about this at the Apple Store last evening and was told that if I download MacOS 27 it will clear out the System Data bloat. Can anyone confirm that's the case?

It is not the case.

I know just updating within the current MacOS 26 keeps all that bloat. Is it different when downloading a whole new OS?

Installing a new OS will only make it worse.

As neuroanatomist describes, there were some changes in macOS 27 regarding storage. But these changes only affect how the storage is displayed. I've seen a number of people post on this forum being upset that they installed macOS 27 and lost a lot of free storage. But it turns out that macOS 26 simply wasn't being truthful. They never had that much free storage to being with and macOS 27 is being a little more honest about it - but only a little.

I'm at the point where I'm wondering if I need to get a new computer and drag my files over and reset my preferences and start over (ugh), but if just updating to MacOS 27 will help, I'd rather wait on the new machine.

With a 500 GB hard drive, you should be able to get storage to a manageable level. Usually this problem is caused by running out of free storage. Note that neuroanatomist says that 20-25 GB is an absolute minimum. Most people reading that will take it the wrong way. You need 100 GB of free storage for optimum performance and reliability. Once you get down to 50 GB free storage, you'll start to experience performance problems and this "System Data" bloat.

25 GB is enough to download a new version of the operating system. That's all most people care about these days. They're addicted to these updates. But 25 GB is an absolute minimum. It would deliver a very poor experience. You want 100 GB free. Since you're still running macOS 26, what you're seeing as "available" storage isn't free. In macOS 26, "available" is still a fantasy. Most likely you are simply out of free storage.

You'll need to download a 3rd party storage management tool to get control over it. I can't recommend one because I develop one and I'm not allowed to post a link to it. If I thought the other storage management tools were great, then I wouldn't have written my own in the first place.

You need to see which of your folders is taking up too much space, and delete the files that are causing it. Hopefully, these are your files to delete and you can simply copy them to an external hard drive for safekeeping. If the files are in some hidden system folder, then I recommend asking here before touching them. Some files aren't safe to delete and people tend gravitate towards those options that do the most damage, for the least impact.

steve626 wrote:

I have several Macs in use and "System Data" ranges from 40 GB to 100 GB on these Macs, which are on OS from Monterey to Tahoe. The MacOS itself on one of the Tahoe machines takes about 20 GB.

If/when you update a Mac to Golden Gate, System Data will very likely increase. On my personal Mac (16" M4 Pro MBP, 2 TB internal storage), System Data ranged from 9-40 GB before upgrading that Mac from Tahoe to Golden Gate. On Golden Gate, System Data ranges from 120-160 GB. So I can see where the term 'bloat' seems applicable.

It's not, technically. Still the user's data, macOS just changed the accounting method for space calculations ('purgeable' space is not separately reported, those data are now counted with System Data).

mhb wrote:

I appreciate the help so I can understand all this better. You can see my reply to neuroanatomist for an update. I definitely want more free storage than 20-25 MB. What's most frustrating is that I read that System Data should only be, say, less than 25 GB

That is the size of the macOS system and is accounted for elsewhere. “System Data” is not the OS and may not even be “system” data. It will fluctuate and there isn’t any size metric you can hang your hat on. As neuroanatomist already described, the System Data category is a catch all for things Spotlight doesn’t recognize or does not fall into the other Storage categories. It was actually once called “Other,” but that was too confusing so they renamed it “System Data.” Clears it right up, doesn’t it?

The “system” data that usually takes up most of the space is local Time Machine snapshots. That builds up if you have a Time Machine backup that you don’t backup to regularly.

Another common problem with clearing storage is deleted files. SSD’s cannot make deleted space available instantly. It may take overnight to reset the storage to make it writable. That process is slowed if you have little free space. “Free” and “Available” are not the same. Free is a subset of Available. The free space can be seen in disk utility. If you have very little free space, pick a few large things to delete that are smaller, in total, than the free space, then leave your Mac on and go to bed. Hopefully the deleted space will be reset in the morning and you will have more free space.

No it won't I updated to Mac OS27, I did and now I have 250gb of system data and Apple can't help or are able to get rid of it, in fact they say it's not a problem. I only have 100gb left on my Hard drive.

mhb wrote:

What's most frustrating is that I read that System Data should only be, say, less than 25 GB

Where did you read that? The internet? The internet's not true.

System Data should be whatever is appropriate for your computer. Every computer is different.

The most important thing to remember here is that "System Data" is simply a field on that atrocious System Settings > Storage display. Don't even go there. It's worse than useless. All it does is confuse people. This screen isn't what people think it is.

Primarily, this is a Spotlight aggregator. Spotlight searches your computer and categorizes each file as "something" - documents, videos, books, mail, messages, music, etc. Only there is no "etc". That's "System Data". Much of the data put into this category may have nothing whatsoever to do with the operating system.

For example. I'm a developer so I have lots of relatively unusual software. I also have a "Developer" category for 15 GB. But I have some virtual machines installed too. Those account for part of my 106 GB System Data. For me, that's perfectly normal.

I haven't seen anything so huge that it will make a difference if I delete it

But do you know where to look? Most of this data is in hidden directories. There are many, many hidden directories on your computer. There's nothing that Apple likes more than hidden directories.

so it must be large amounts of small files

It is not.

I can't freely delete without potentially causing issues. Or, likely, I'm still missing something basic.

All I can do at this point is refer you to what I've already posted. Every computer is different. If anyone on the internet tells you with any confidence that it's definitely X, Y, or Z, they are definitely lying to you. The operating system has become hopelessly complicated. Your hard drive is unique in the universe. They say that every time you shuffle a deck of cards, the order is unique in all of existence. There are 52 cards in a standard deck. There are hundreds of thousands of files on your computer.

I have 170GB of System Data bloat with over 225GB of free disk space on macOS 27.0.1, so it just bloats regardless. And mine is brand new, only 10 days old. That only shows when my external SSD is plugged in. Immediately after ejecting it, System Data drops to 67GB.

Apple engineers advised me that macOS is creating one snapshot in case my external APFS drive becomes corrupt or isn’t ejected properly. They ran full diagnostics, and that’s what they reported back to me.

So according to them, it’s completely normal, but IMO, it’s ridiculous. They could easily fix this, or maybe they just aren’t smart enough to properly label everything and be transparent. Who knows? 😂

It’s annoying, and yes, it’s purgeable space, but you shouldn’t have to buy a brand-new computer only to have macOS automatically take up a huge chunk of your storage and then basically say, “Well, you can have it back once your hard drive starts running out of space.”

I think that’s ridiculous. That’s just my opinion, though.

melvin3v wrote:

In my case, CleanMyMac and DaisyDisk were unable to locate the hidden System Data.

CleanMyMac can be poison for Macs. I would uninstall that completely, and then search for leftover remnants and delete those as well.

Tools like DaisyDisk or Stereograph won't find anything called "System Data." That is an accounting label Apple uses for a wide range of items. No folders are actually called "System Data." However those tools will enable you to track down where every bit of your used file space is on your Mac. Including space used on the internal drive as well as on the external drive.

I migrated from an M1 MacBook Air with only a 256GB SSD annd 109gb free and there’s hardly anything on either computer. My Mac mini has a 512GB SSD with about 225GB free, yet System Data jumps to around 165GB whenever my external SSD is plugged in. As soon as I unplug it and reopen Storage settings, System Data drops back down to around 60GB.

So with 512 GB SSD and 225 GB free, you are using 287 GB on that drive. Is that what you expect? If you expected to be using less, use DaisyDisk or Stereograph to do an audit to find out exactly where your disk space is going. Then you can decide what to do about that. Be careful before deleting system files or files in hidden directories, however.

CleanMyMac may have corrupted the internal accounting on the Mac so it is not clear to me if this is fixable without a complete wipe, clean reinstall, and then bringing over only files and accounts but no settings and no apps (reinstall the apps fresh).

rranger wrote:

For some bizarre reason beyond my comprehension, Apple makes a copy of the backup on the internal drive, which creates ridiculous amounts of "System Data." Why, I ask rhetorically, am I making an external backup if I want a copy on my Mac?

That's not how it works. Maybe you read this somewhere on the internet or in Reddit or got it from ChatGPT. But it's not correct and your post is perpetuating incorrect information. Apple does not make a copy of the backup on the internal drive. What is done is that, in between backups [which can be every hour, or some other interval, or less often if the user disconnects the backup drive(s) for a while], the Mac records changed files inside "snapshots" that are kept on the Mac while waiting for the next backup. This is so if you need a backup to recover a lost or corrupted file after the last backup was done but before the next one is run, it can be recovered from those interim "snapshots." Those snapshots are usually quite small -- one exception could be if massive files are being modified and are waiting to be backed up, such as virtual machine files or huge videos. So no, your Mac does not "copy the backup onto the internal drive," not at all. Those snapshots also help the next backup to run efficiently and quickly as they have done a lot of the "work" for the backup ahead of time. After the Time Machine backup is done, snapshots are deleted but then new ones get created as more files are created or modified in between backups.

tbirdvet wrote:

External drive increased my system data and I have no other items that would cause this. I made no changes between OS26 and OS27. I show a difference of >10GB with my external TB5 drive on vs off.

Is that external drive also being backed up along with the internal drive, to a separate Time Machine drive? If so, there may be snapshots being generated from that external drive's contents and those snapshots might be included in the "System Data" accounting bin.

In my case, CleanMyMac and DaisyDisk were unable to locate the hidden System Data. I migrated from an M1 MacBook Air with only a 256GB SSD annd 109gb free and there’s hardly anything on either computer. My Mac mini has a 512GB SSD with about 225GB free, yet System Data jumps to around 165GB whenever my external SSD is plugged in. As soon as I unplug it and reopen Storage settings, System Data drops back down to around 60GB.

Apple engineers told me this is normal behavior, which is frustrating. They were pretty firm in their explanation that macOS 27 creates a hidden snapshot in case the external SSD becomes corrupted or is improperly ejected. Whether that’s BS or not, I have no idea, but they spent a 3 days investigating before getting back to me with that explanation or that’s at least when supervisors responded 👍 And this is Os27 for me OP is on Tahoe I beleive.

So that’s been my experience, which is a little different from OP’s. Hopefully Apple can figure out a different method someday 😂 I would think with AI etc they could easily identify okay this is 3rd party cach, document then just show at least what type of files they are and if should remove or not even clean my Mac does that.

mhb wrote:

...I'm starting to think that they way I function in 2026 -- not just the browser -- is just going to require a lot more disk space for "System Data" than six years ago...

Again, "System Data" is just a catch-all for stuff Spotlight doesn't assign to a specific category. Spotlight itself is not perfect. On my work Mac, the cloud storage service we use keeps a local cache of 200 GB, and Spotlight adds that to the Applications total.

But it's very likely that you're going to require more storage today than you needed 6 years ago, and even more 6 years from now. That's the way technology works.

This is Get Info on a RAW image from my camera:

One picture, it's a 28 MB file. This is the type of Mac that I used from 1987 to 1993:

The red box highlights that instead of the base model with two floppy drives, I sprung for the upgraded model with a 20 MB hard drive. What could store an operating system, lots of applications and thousands of files decades ago couldn't hold a single picture that I take today.

The alternative is getting a software program to help, which can be a bit of a crapshoot if you're not familiar with these and some are dodgy.

What you need to manage are the things you can easily manage – photos, videos, music, email and text message attachments, etc. Trying to manage cache files, profiles, etc., is a useless exercise in frustration.

Since you cannot add internal storage to most Macs, buy more than you think you'll need at the outset. Then manage as you go. I have a 227 GB Photos Library and 300 GB of 'Documents' (of which 150 GB is actually my iMovie Library, and a lot of the rest are RAW images, which Spotlight calls documents not photos). Most or all of that could be moved to external storage. For example, I only keep a couple years of RAW images on my Mac, the several hundred GB of older ones are stored externally. Since I got this Mac with 2 TB of internal storage, I have plenty of space.

My System Data didn't change over night after all that material removal yesterday.

The intent there was to clear more free space, not necessarily reduce system data. Did your free space increase? How much free space do you have as indicated in disk utility?

have you attempted to remove the time machine snapshots from disc utility?

Wasn’t true for me I just worked with Apple support for a week regarding system data bloat on brand new Mac Mini. Mine kept climbing by 10gb daily up to 167gb system data on a 512gb SSD it’s maddening. They said it’s fine and supposed to do this? everytime I plug in non Time Machine external ssd system data climbs to over 160 and when I unplug it drops to 60gb I’ve never experienced this but it’s frustrating to buy brand new system and for Mac to take hostage 100gb IMO.