01 The short version
GrandPerspective and Delve both draw a treemap, and both are
free. GrandPerspective is open source under the GPL, lightweight,
and runs on Intel Macs and macOS versions going back many years.
It's a tool that earned its trust.
Delve is the newer, heavier-engineered version of the same idea:
the treemap is drawn on the GPU and stays smooth across millions
of files, on-disk size sits next to logical size with APFS
clones counted once, and it plugs into Spotlight, Shortcuts, and
Quick Look. The trade: it needs macOS 26 and Apple Silicon, and
it isn't open source.
03 Where GrandPerspective wins
It's open source, so you can read exactly what it does to your
disk, and that matters to a lot of people, us included. It runs
on Intel Macs and on macOS versions that Delve flatly won't
launch on, so for an older machine it isn't even a contest. It's
small, fast to open, and it has earned years of trust doing one
job well. If any of those are your constraints, stay with
GrandPerspective with our blessing.
04 Where Delve wins
The picture is drawn on the GPU, so panning and zooming a
million-tile map stays at 60 Hz instead of stuttering. The
numbers are honest about APFS: on-disk size next to logical
size, clones and hardlinks counted once, so you don't delete a
folder expecting 80 GB back and recover 12. And it behaves
like a 2026 Mac app, with Spotlight, Shortcuts, Quick Look, full
keyboard and VoiceOver support, and native chrome. The
how-it-works is in the
build notes.
Our honest recommendation
On an older or Intel Mac, or if open source is a hard
requirement: GrandPerspective, no hesitation.
On Apple Silicon with macOS 26, if you want the same picture
drawn faster with honest on-disk numbers and modern
integration: Delve. Both are free, so it's an easy thing to
try.