Right-click ~/Pictures/Photos Library.photoslibrary in Finder and choose Get Info, and you may see a number that does not match what you expect — sometimes far larger than your iCloud storage plan, sometimes surprisingly small even though you have thousands of photos. Both are normal, and both come down to the same setting: whether Photos is keeping full-resolution originals on your disk or space-saving previews it can replace on demand. This article explains what is actually inside that package in general terms, how the "Optimise Mac Storage" setting changes what gets stored locally, and the correct way to reclaim space from Photos — which is never by opening the package and deleting things by hand.
What's inside the Photos Library package
Photos Library.photoslibrary is a macOS package: a folder that Finder displays as a single file. Opening it (via right-click → Show Package Contents) reveals an internal structure that Photos manages entirely on its own. In general terms, it holds the original image and video files you imported or captured, a set of derived versions — smaller previews and thumbnails that Photos generates so it can display your library quickly without decoding a full-resolution RAW or video file every time — and a database that tracks every photo, edit, album, face, and piece of metadata, along with how everything relates to everything else.
The exact internal layout is not something Apple documents for outside use, and it changes between macOS versions. That is the reason to treat the package as opaque: Photos, not Finder, is the only thing that should ever modify what's inside it.
Originals on disk versus "Optimise Mac Storage"
If you use iCloud Photos, you have a choice of how much of your library actually lives on your Mac's disk:
- Download Originals to this Mac keeps every full-resolution photo and video on your local disk, in addition to iCloud. Your library on disk is the same size as your full photo collection.
- Optimise Mac Storage keeps space-saving previews locally and stores full-resolution originals in iCloud, downloading a given photo or video's original in the background whenever you open it — provided you are online and signed into the same iCloud account. Thumbnails and previews stay instantly available even offline; a full-quality original for something you have not opened recently may need a moment to download the first time.
Optimise Mac Storage is the setting that makes it possible to carry a photo library far larger than your disk, at the cost of needing an internet connection the first time you want a given original at full quality.
Checking and changing the setting
The toggle lives in Photos itself:
- Open Photos.
- Go to Photos → Settings → iCloud.
- Choose Download Originals to this Mac or Optimise Mac Storage.
Switching to Optimise Mac Storage does not delete anything from iCloud — it only changes what Photos keeps cached locally, replacing local originals with previews over time as it needs the space back. Switching the other way starts downloading full originals for everything in your library, which can take a long time and use a large amount of disk space and bandwidth on a big library.
Why the library can still look huge with Optimise on
Optimise Mac Storage reduces disk usage, but it does not shrink the library to a token size. Previews still have to be good enough to display and edit against, so a library of tens of thousands of photos and videos can still occupy tens of gigabytes even fully optimised. Recently viewed or edited items are also more likely to have their full originals downloaded and cached locally, since Photos assumes you might want them again soon. And any edits you have made are typically stored in addition to the original, since Photos preserves your ability to revert to the unedited version.
The number Finder shows for the whole package is also inherently a single figure for everything Photos manages — originals, previews, edits, and the database together — so it will not obviously correlate with "number of photos" the way people expect.
Why you should never dig into the package by hand
It is tempting, when a package look large, to open it and start deleting files that look unnecessary. With a Photos library this is a genuinely bad idea. The database inside the package tracks every item by reference — its location, its edit history, which album and face and moment it belongs to — and removing or moving files directly breaks those references without Photos ever being told. The result ranges from missing thumbnails to a library that Photos can no longer open cleanly. There is no supported way to safely trim a Photos library from outside the app, and no storage tool, including VolumeLens, should try to reach inside a .photoslibrary package and modify its contents.
The correct way to free space: delete inside Photos, then empty Recently Deleted
The only safe way to reduce what a Photos library actually needs to store is to remove photos and videos through Photos itself:
- Select the items you no longer want, in the Photos app.
- Delete them (Photos moves them to the Recently Deleted album rather than removing them immediately).
- Go to the Recently Deleted album and empty it, either item by item or all at once, once you are sure you want them gone.
Recently Deleted holds items for about 30 days before Photos removes them automatically, which gives you a safety window if you change your mind. If you want the space back sooner than that, emptying the album manually is what actually triggers the underlying storage — including any iCloud copy — to be released. Deleting through the app is also the only way that correctly updates the database, removes the associated previews and cached originals, and keeps every other library reference consistent.
Conclusion / VolumeLens tie-in
The Photos library is one of the few places on a Mac where the right move is deliberately not to go digging with a general-purpose storage tool. It looks large for reasons that make sense once you know them — previews, cached originals, edit history, a database tying it all together — and the only safe lever for shrinking it is the one Photos itself provides.
We built VolumeLens because we needed a Mac storage tool to be honest, fast, and safe about the limits of what it should touch, not just the things it can show you. VolumeLens will show you the size of Photos Library.photoslibrary as a single honest total, the same way Finder does, so you can see how much of your disk it occupies — but it treats it as a package to report on, never one to open and edit, because that decision belongs to Photos and to you. Start with VolumeLens to see where a library like that stands next to everything else on your disk, then use Photos' own settings and Recently Deleted album to actually change its size.