How to clean junk and duplicate files on MacBook Pro

A quarter of a terabyte is certainly adequate free space for normal usage.

For a quick cleanup: Perform a Safe Mode start, then a normal start. This will clean up and rebuild various caches.

Empty the trash too, if that isn’t set to happen automatically on your Mac.

A tool such as OmniDiskSweeper will help you identify the largest unnecessary or duplicated files, or the largest files that can best reside elsewhere, and you can then work through the files from largest to too-small-to-bother-with smallest to have the maximal usual reduction with the minimal effort.

I am aware of some APFS-based duplication-detection and deduplication apps that are using the APFS copy-on-write feature, but I have not and will not be testing those on live systems with real data, and will accordingly not recommend any of them. One the of deduplication tools available here reportedly has a window where there is no file on persistent storage; a short time within the file deduplication process, where failures or outages during that window can lead to file loss. Others hopefully lack this window.

This whole deduplication process can be subtle, too. I would be concerned about what happens when different duplicates are deduplicated and then one clone is subsequently modified, for instance. What should happen then? All file clones get modified? Just one? Do all time and date stamps get modified, or just one?

Whether / if / when Apple might enable their own APFS deduplication tools? (Request it.)

As for add-on cleaner apps, I would typically not suggest using any of those. More subtly, the efforts of such apps to “free” memory and “free” storage can actually be wasteful of what you paid for, preventing it from helping your performance. And some have occasionally introduced corruptions.

Have a complete backup before you start your quest for storage usage reduction, too.

donl1155 wrote:

That does surprise me on the 'cache' vs 'junk' but I get what you mean there. As for the apps that supposedly clean the machine, yes I have no intention of buying one of those.

But as far as duplicate files, I am sure I have duplicates of photos. I often times have downloaded a picture from somewhere or somebody into my Download folder and then copied it to a different folder and then imported it into the Photos app. Certainly I have created that part of the problem myself but want to know how to find those types of things and then delete those that I don't need.

If you believe you created duplicate files by downloading them to your Downloads folder and then copying them elsewhere, one thing you can do is examine your Downloads folder and delete all its contents, or at least the files/folders inside Downloads that you no longer (or never) access from that folder. Downloads also tend to accumulate .dmg files from installers, or other installer files, and all installers can generally be re-downloaded if necessary. Any installer file more than a year old is likely out of date anyway and should be deleted.

As has been pointed out by others, with APFS copying files often takes no additional space because APFS knows it is a copy and is efficient about that.

Another thing you can do is look in your major folders and list the files and folders by size. Only large files/folders will impact your free space so you need not waste time on smaller files.

If you receive Messages on your Mac, this Apple support link provides instructions for deleting big space users:

Delete messages and conversations in Messages on Mac - Apple Support

It includes guidance on deleting specific large attachments in Messages. The built in Mac Storage tool (accessed via Settings) can also do this.

One of the features of Apple File System (APFS) is that in most cases, when you attempt to create a duplicate of a file, the System creates pointers to the original file instead of replicating the data blocks. Only ONE original is retained, and all others reference that original. The amount of space occupied by most duplicates is ZERO.

Deleting the original just re-arranges the pointers if there are multiple references to that same original. Only at the point where you request to modify one of the "duplicate copies" do the blocks actually get replicated, because now it is no longer a bona-fide duplicate. (This is called 'copy-on-write'.)

That is why there is extra complexity in the technical answers you have received to date.

Generally speaking, your "duplicates" are not consuming ANY storage space. Deleting them will not be productive and could be harmful.

Note: This general description holds for Files on the same Volume. Files on different Volumes may be treated differently.

donl1155 wrote:

But as far as duplicate files, I am sure I have duplicates of photos. I often times have downloaded a picture from somewhere or somebody into my Download folder and then copied it to a different folder and then imported it into the Photos app. Certainly I have created that part of the problem myself but want to know how to find those types of things and then delete those that I don't need.

Look through your photos and delete any that you don't want. I'm willing to bet there are more AI-powered duplicate photo finding apps than there are duplicate photos on your computer.

But you do get credit for a scenario where duplicate files actually are possible. Normally, on macOS, duplicate files aren't even possible. Most "duplicate" files are clones that don't take up any extra space. One of the few ways to actually get duplicate files is to copy the same data to your computer multiple times. Photo imports are a good way to do that by unchecking the "Ignore already imported photos" button that's checked by default.

donl1155 wrote:

I know there is a lot of junk files & duplicate files I am sure. 

How do you know this? Please explain without using advertising from software apps selling scam junk file removal.

How do I go about cleaning & deleting those files?

Would it surprise you to learn that those most of those "junk files" are cache files that make your computer run faster? Not to worry, the same companies that sell those "clean up" scams also have "boost up" subscriptions available for the low, low price of $49.99 per month.