Storage guide

Why external-drive and iCloud storage sizes can differ

By learnhubplay · Practical checks and clearly labelled Tend features

Finder, a folder scan, and a disk-capacity display can show different totals without any of them describing the same measurement. Before moving or deleting data, identify which number answers your question.

Separate the three questions

• Logical file size: how much data a file reports containing. A folder scan can add these sizes, including metadata for files whose contents are not local.
• Allocated storage: space the filesystem currently assigns to data. Sparse files, compression, hard links or shared blocks can complicate the total.
• Volume free space: what the filesystem reports as currently available on a particular volume. Other folders and applications affect this reading.

There is no generally safe rule that subtracts one of these totals from another and calls the remainder reclaimable. Check which metric the tool reports and whether the scan was complete.

Review external drives as separate sources

Identify the drive, selected folder and available capacity before scanning. If a drive disconnects, a folder path or familiar volume name alone does not establish that the same source has returned. Reconnect the intended drive and refresh the reading before acting.

File systems and enclosures expose different information. A missing SMART field is not a healthy verdict. Network folders may have delayed or limited capacity information, and access restrictions can prevent a full inventory.

Cloud placeholders can look large without local contents

iCloud Drive can keep items available through the cloud while changing what is downloaded to your Mac. A filename and size in Finder do not, by themselves, prove that the contents are ready offline. Check Finder's availability/status information and the provider's supported controls.

Downloading contents can consume space and bandwidth. Deleting an item in a synced location can affect the cloud copy and other devices. If your goal is to keep the original online while changing local availability, use the provider's download/removal controls rather than assuming Trash is a local-only action.

Read Tend's coverage labels

Tend's Storage explorer reviews folders you choose or can access, shows coverage gaps, and does not delete from the explorer. File Provider placeholders can report sizes without local contents; those totals are neither locally allocated bytes nor a complete account of cloud storage.

Quick Look is an explicit preview action. A cloud provider may need to make contents available to display a preview. Keep metadata-only inspection separate from opening or downloading a file when working offline or with limited bandwidth.

A useful check before a large copy or export

1. Identify the actual destination volume and refresh its free-space reading.
2. Check whether source contents are downloaded and accessible.
3. Allow for both the output and temporary working files required by the application.
4. Avoid adding two free-space readings from folders on the same volume.
5. Make a small copy or export first, then review the application result.

A capacity estimate cannot guarantee an export will finish. Permissions, file availability and application behavior still matter. It can help reveal a shortage before you begin a long job.

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