iCloud and cloud storage

Files that are only pretending to be here

Updated 2026-08-08 · 5 min read

Finder shows the file, Get Info shows the size, and the bytes are not on the machine. Placeholder files are how every cloud service fits a terabyte of storage onto a 256 GB laptop, and they quietly change what 'my files' means.

The mechanism

With optimisation on, a cloud client keeps recently-used files local and evicts the rest, leaving a placeholder: the name, the metadata, a thumbnail — and no content. Opening one triggers a download; on a plane, it triggers an error.

Each service shows it differently: iCloud Drive puts a cloud badge next to the name, Dropbox calls it *online-only*, OneDrive *files on-demand*. Same idea everywhere.

How to tell what is real

The honest measure is disk usage versus logical size. In Terminal:

du -sh ~/Documents/BigProject
ls -lh ~/Documents/BigProject

du reports what is physically present; ls reports what the files claim to be. A 40 GB folder occupying 200 MB of disk is placeholders nearly throughout. iCloud's evicted files are also visible by name — Finder hides it, but the on-disk entry for an evicted report.pdf is .report.pdf.icloud.

What placeholders break

• Search by content. An evicted file's text is not on the disk, so nothing

local can search inside it. Names still match; contents cannot.

• Backups. Time Machine copies what is local. A backup made while most of

the library was evicted contains placeholders, not photos — discovered, in the worst version of the story, at restore time.

• Airplane work. The proposal you *have* is a 40 KB stub.

Controlling it

Per-service: iCloud's Optimise Mac Storage checkbox (System Settings → Apple ID → iCloud Drive), Dropbox's per-folder *Make available offline*, OneDrive's *Always keep on this device*. The pattern that works: let the bulk optimise, pin the folders whose absence would hurt — current projects, the tax archive, the things backups must actually contain.

Before travel or a backup you intend to trust, force the download: select the folders, right-click, and use the service's download/keep-offline action, then confirm with du that the bytes arrived.

Common questions

Do placeholder files count against my disk space?

No — that is their purpose. They occupy kilobytes locally while the content occupies quota in the cloud.

Does Time Machine back up online-only files?

It backs up what is on disk, which for an evicted file is the stub. Download folders you need durable before trusting the backup.