How macOS actually works

Three ways one file wears two names

Updated 2026-08-08 · 5 min read

All three make a file appear in two places. They differ in what happens when the original moves, when it is deleted, and when a program that does not expect links walks into one.

Aliases: the Finder's link

Right-click → Make Alias. An alias is a small file that Finder resolves, with a trick the others lack: it tracks its target by identity, so moving or renaming the original does not break it. The cost: aliases are a Finder concept. Terminal and most Unix tools see an odd little file, not a path to follow.

Symbolic links: the Unix link

ln -s /path/to/original /path/to/link

A symlink stores a *path*, and everything Unix-side follows it transparently — which is why development setups lean on them. Move the original and the link dangles; delete it and the link points at nothing. Finder follows symlinks happily, so they are the general-purpose choice.

Hard links: the same file, again

ln /path/to/original /path/to/link

Not a pointer — a second directory entry for the *same underlying file*. Equal in every way; delete either name and the other keeps the data alive. Only the deletion of the last name releases the file. Limits: same volume only, and not for folders. Legitimate uses are narrow (deduplicating identical files without losing either name); backup tools historically leaned on them heavily.

What breaks, what to use

	Original moved	Original deleted	Terminal follows
Alias	still works	breaks	no
Symlink	breaks	breaks	yes
Hard link	n/a — same file	survives	yes

Practical defaults: symlinks for anything touched by scripts or dev tools, aliases for Finder-only convenience, hard links only when you can say why.

Seeing what you have

ls -l marks symlinks (l in the mode, arrow to the target). Hard links show in the link count column (second field of ls -l greater than 1). Finding all of either across a disk is a search-tool job — and link-heavy folders are a classic source of double-counted disk usage, which is why size audits sometimes disagree with the finder of fact, du.

Common questions

Which link type should I use for a folder?

A symlink — hard links cannot target folders, and aliases only work in Finder. ln -s handles folders fine.

Do links duplicate disk usage?

No. All three reference one copy of the data; only naive size scans that follow links count it twice.