Understanding storage
Understanding storage
Hard links, sparse files, APFS snapshots, and why your disk numbers never quite agree.
Storage vs Disk Space vs Drive Space on Mac: Are They the Same Thing
Storage, disk space, and drive space get used interchangeably on Mac, but the terms differ, including the decimal-versus-binary gap behind advertised capacity.
August 28, 2026·Read →
APFS Clones Explained: Why Duplicating a Huge File on Mac Is Instant
Duplicating a file on APFS creates a clone sharing the same data blocks as the original, which is why it is instant and free until either copy is edited.
August 19, 2026·Read →
How Spotlight Indexes Your Mac: mdworker, mdimporter, and mdfind Explained
Spotlight's indexing pipeline relies on mdworker, mdimporter plugins, and the mdfind, mdimport, and mdutil commands — here is how each piece fits together.
August 15, 2026·Read →
What Is .fseventsd on Mac and Why Does It Exist on Every Volume
.fseventsd is a hidden per-volume log of filesystem changes that Spotlight and Time Machine rely on, safely rebuilt by macOS if it goes missing.
August 7, 2026·Read →
du vs df on Mac: Why the Two Commands Never Quite Agree on Free Space
du and df measure Mac storage differently, one from the filesystem and one by walking folders, which is why their numbers disagree and which to trust.
July 27, 2026·Read →
Treemap Visualisation for Mac Storage: Why It Beats a Sorted List
What a treemap is, why it finds the biggest thing on your disk faster than a list, and why drill-down treemaps beat one flat map of a whole disk.
July 25, 2026·Read →
Mac Storage Terminology Explained: SSD, Volume, Snapshot, and More
A plain-language dictionary of Mac storage terms — SSD, volume, container, snapshot, purgeable space, sparse file, hard link, symlink, and extended attribute.
July 20, 2026·Read →
Purgeable vs Available Space on Mac: What the Storage Screen Doesn't Say
Purgeable space on Mac counts as used but is really reclaimable. What feeds it, why it exists, and why it can mislead you about how full your disk is.
July 18, 2026·Read →
How macOS Actually Calculates Free Space (And Why the Number Lies)
Why the free space number in Finder rarely matches what you expect: reserved space, purgeable data, shared container pools, and the GB versus GiB gap.
July 14, 2026·Read →
Snapshots vs Backups on Mac: What an APFS Snapshot Actually Protects
APFS local snapshots and real backups solve different problems. Here is what a snapshot actually is, how Time Machine uses it, and why you still need both.
July 12, 2026·Read →
APFS Containers and Volumes: Why Your Mac's Disk Isn't Really Partitioned
How APFS containers and volumes work on Mac, why volumes share one free space pool instead of fixed partitions, and how to add a new volume from Disk Utility.
July 6, 2026·Read →
The com.apple.quarantine Flag: What Sets It, and What It Actually Means
How macOS decides which files get the com.apple.quarantine attribute, what Gatekeeper does with it on first launch, and how to remove it deliberately.
July 4, 2026·Read →
Symbolic Links vs Hard Links on Mac: What Each One Actually Costs in Space
How symbolic links and hard links differ on macOS, why one costs almost nothing in storage while the other costs the full file, and where Finder aliases fit in.
June 26, 2026·Read →
Nominal size vs on-disk size on Mac: two numbers every storage tool should show
Why a file's nominal size and its on-disk size can differ on Mac: allocation blocks, sparse files, transparent compression, and why both numbers matter.
June 20, 2026·Read →
Why Finder's Get Info size doesn't match the Storage settings number on Mac
Why Finder's Get Info size and the Storage settings figure for the same folder disagree: app bundles, purgeable space, APFS snapshots, and metadata overhead.
June 15, 2026·Read →
APFS transparent compression explained: files smaller than they appear
How APFS transparently compresses certain files, the com.apple.decmpfs attribute that marks them, and why their on-disk size can be smaller than a naive total.
June 12, 2026·Read →
Sparse files on Mac: why a file's size and its disk usage can differ
What a sparse file is, why its nominal size and allocated size diverge, where they show up on macOS, and how APFS handles the holes inside them.
June 11, 2026·Read →
Hard links on Mac explained: what they are and why deleting one doesn't help
A clear explanation of hard links on macOS: how they work, how to see and trace them with ls and find, and why deleting one copy doesn't free any space.
June 6, 2026·Read →
How a Mac App's Size Is Actually Measured Inside Its .app Bundle
What's really inside a Mac .app bundle, why code signatures and universal binaries add to its footprint, and how to read an app's true size on disk.
June 3, 2026·Read →
Extended Attributes on Mac: The Hidden Metadata Attached to Every File
What extended attributes are on macOS, how Finder tags and quarantine flags use them, how to list them with xattr, and why their cost adds up at scale.
May 30, 2026·Read →