Understanding how iCloud Photos optimizes photo storage and keeps your originals

Apple makes it possible to have thumbnails of a much larger media collection, but always retains the full-resolution versions.

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The old saw about one’s eyes being larger than one’s belly surely applies in an era when we can capture multi-megabyte images and gigabyte videos and have infinite storage online—but still have to contend with the size of flash drives in iPhones and iPads and SSDs in Macs.

Apple squared that circle with iCloud Photos, one of many companies’ attempts to pair cloud storage and personal or professional media capture. With Google Photos, Google stores everything in your cloud account and uses its native and browser-based apps as glimpses into that storage. Apple, in contrast, wants you to have a sort of copy of all your images available offline and online with iCloud Photos.

For devices that lack enough storage to keep full-resolution versions of images and videos, Apple lets you enable optimized storage. That’s found in iOS in Settings > account name > iCloud > Photos and in Photos for macOS in Photos > Preferences > iCloud. With that setting enabled, your device always retains a thumbnail of all your media and keeps all the associated metadata. When you want to view a photo or movie, tapping it or double-clicking it downloads and caches the full-resolution version.

But Apple never dumps your original image. Optimization happens after whatever device has captured or imported an image or video has uploaded it completely to your account at Apple’s iCloud servers. Apple doesn’t reveal exactly how it handles redundancy, but it’s likely that until your media is copied to multiple geographically disparate locations across Apple’s data center network, the full-resolution version of the image or video remains on that originating device.

After that, your device’s operating system balances available storage with retaining cached copies of the high-res versions of your media. If it needs to free up storage, those much-larger renditions are dumped, with the OS secure in its ability to retrieve it again as needed.

This Mac 911 article is in response to a question submitted by Macworld reader Theresa.

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