Where did all my disk space go?

You didn't install a single new app this month. You didn't shoot 4K video. And yet “About This Mac → Storage” says you have 12GB free out of 512GB. This is one of the most common — and most confusing — states a modern Mac ends up in, especially for developers.

The honest answer is that Apple's own storage tool isn't built to help you here. It gives you a rough category breakdown (“System Data,” “Other”) and no way to drill in, sort, or act on what it finds. It's read-only by design.

On a typical developer or power-user Mac, disk space rarely disappears into one big obvious file. It disappears into thousands of small, invisible ones, spread across a handful of categories:

Every item on that list lives several folders deep, often inside ~/Library, which Finder hides by default. None of it shows up when you scroll through your Applications folder looking for something to delete. And because each individual folder might only be a few hundred megabytes, no single one feels worth investigating — until they add up to tens or hundreds of gigabytes.

The fix isn't a bigger drive. It's actually being able to see where the space went — sized, sorted, and grouped by what's actually using it — before you decide what to remove.