I started with a simple request: help me free up space on my Mac.
My first thought was cache files. As a developer, I install tools, run builds, test apps, and move between projects. I expected a few temporary folders to be taking up space.
What we found was bigger than that: an installed Unreal Engine version I no longer needed, dozens of simulator devices, multiple iOS runtimes, and an old Codex backup that had quietly kept about 13 GiB of data.
By the end of the cleanup, my Mac reported 102 GiB of available space. That is the final free-space reading, not a claim that we recovered 102 GiB in this session.
Here is how I used Codex to understand what was taking up space, decide what to keep, and remove what I no longer needed.
I Thought It Was Just Cache
My initial request was about clearing cache files. Then I asked Codex to check the whole computer and tell me what was taking up space.
That changed the conversation.
Instead of treating every large folder as something to delete, we started looking at what each folder actually contained. Was it temporary data? An installed tool? A project? A local copy of something synced elsewhere?
One of the first big items was Unreal Engine 5.8, listed at 46.3 GB. I decided I no longer needed that installation and asked to remove the Epic Games files and local projects too.
There was a meaningful distinction with one project stored in iCloud Drive: removing its downloaded copy would free local space, while deleting the project would remove it from iCloud and synced devices. I chose to delete that project everywhere.
That was my first useful lesson from the cleanup: “free up space” is a broad request. The right action depends on whether I want to keep the underlying work.
The Biggest Surprise Was My Development Setup
The simulator inventory was the part that made me pause.
It showed roughly 85.8 GB across iOS runtime images, device data, and shared caches. There were 56 simulator device folders.
I did not need 56 test devices.
We had to clarify which ones I actually wanted to keep. I initially thought about an iPhone 16 running iOS 18, then confirmed the final selection:
- iPhone 17 — iOS 26.3.1
- iPhone 13 — iOS 18.0
Codex checked the inventory and removed the other 54 simulator devices, along with the unused iOS 18.1 and iOS 18.2 runtimes and their shared caches.
The device folders alone went from about 33.3 GiB to 8.6 GiB—a reduction of roughly 24.7 GiB in reported folder usage. The earlier inventory displayed the starting size as 35.8 GB; those are different units for approximately the same quantity.
We also saw why checking the result matters. Apple’s runtime tool initially reported an image as “Deleting.” Later, it showed only the two runtimes I wanted to keep. Some downloaded assets remained in macOS’s managed storage, so we did not count all of their apparent size as immediately recovered space.
Then I asked about a folder called Codex pretest.
It turned out to be an old backup from October 7, taking up about 13 GiB. It contained old sessions, history databases, archived sessions, packages, and generated images.
Before removing it, Codex checked whether files had changed since the backup was created, whether a running application had files open inside it, and whether current configuration referenced it. Those checks supported treating it as an unused backup, although deleting it still meant giving up that recovery copy.
I approved its removal.
Most of it deleted normally. The final 32 MB contained root-owned plugin files, so macOS required an administrator password. After that step, Codex verified that both the backup folder and its Desktop location note were gone.
The active Codex folder remained in place.
More Space, and a Better Way to Maintain My Mac
The final disk check showed 102 GiB available.
I want to be precise about the numbers because it is easy to turn a cleanup story into an inflated headline. We did not record one reliable baseline before every action in the session. Folder sizes, shared files, and delayed space reclamation also mean I cannot simply add every number together and call that the exact saving.
What we did verify was substantial:
- Unreal Engine: removed an installation listed at 46.3 GB as part of the Epic Games cleanup.
- Simulator devices: reduced from 56 to 2, with about 24.7 GiB less reported device-folder usage.
- Unused iOS versions: removed the iOS 18.1 and 18.2 runtimes and their shared caches.
- Codex pretest backup: removed the old backup, measured at roughly 13 GiB.
- Final available disk space: 102 GiB.
The issue was accumulated development data: tools I had stopped using, test environments I no longer needed, and a backup I had forgotten about.
Codex was useful because I could work through those decisions in conversation. I could ask what a folder was, understand the consequence of deleting it, correct which simulator devices I wanted to keep, and ask for verification afterward.
My role still mattered. I had to decide which tools, projects, and backups I was ready to lose. A large folder alone did not answer that question.
The approach I want to repeat is simple: inspect, decide, remove, verify.
As developers, we spend a lot of time setting up environments. This was a reminder to spend a little time retiring them too. A simulator created for one test or a backup made before an experiment can stay around long after its purpose has passed.
I started by asking Codex to clear some cache. I finished with more room on my Mac—and a clearer picture of what I was keeping on it.