What is a treemap?
Short answer: a treemap shows a hierarchy, such as the folders on a disk, as nested rectangles. Each rectangle’s area is proportional to its size, so the biggest files and folders are the biggest shapes, and every folder sits inside its parent.
How to read a disk treemap
- Area is size. A rectangle twice as large uses twice the space.
- Nesting is the folder structure. A folder’s rectangle is divided into rectangles for what’s inside it.
- Colour adds a second dimension. In DiskTree, colour shows the kind of data, such as code, toolchains, caches or media. Other tools use colour for file type or age.
- Zoom in to go deeper. Open a folder to see its contents fill the whole view.
Try an interactive example with made-up files.
Why treemaps suit disk space
Treemaps were invented for exactly this problem. Ben Shneiderman developed them around 1990 to show what was filling a hard disk, and they’ve been used in disk tools ever since. Later work on “squarified” layouts, which keep rectangles close to square, made sizes easier to compare; DiskTree uses a squarified layout.
Compared with a list sorted by size, a treemap shows folders full of many small files, which a list of big files misses. Compared with a sunburst of rings, rectangles make it easier to judge relative sizes at a glance, while a sunburst shows the depth of the folder tree more directly.
Treemaps in DiskTree
DiskTree draws your disk as a squarified treemap, coloured by kind of data, with real file names and sizes. You can switch the measure to number of files or age, filter by name, reveal anything in Finder and mark items for review. Exploring is free; moving items to the Trash from inside the app is a one-time $14.99 purchase.
See exactly what’s using your space
DiskTree is free to download and explore. For Apple silicon Macs, macOS 11 or later.