The hidden data AI tools leave on your Mac

Why it builds up so fast

A chat app looks small in Applications, but it is a web browser underneath, with a web cache, a code cache and a GPU cache of its own, plus every update it has downloaded. Coding agents go further: they compile and run code to check their work, in scratch folders outside your project, and nothing tidies those folders up when the session ends. Local models add the largest files of all.

Measured on the Mac this app was built on, in September 2026:

• 9.1 GB of abandoned build trees from earlier Claude Code sessions, cleared on 11 September — the single largest item ever reclaimed on that machine.
• 4.5 GB in the Claude desktop app's caches on 5 September, 3.7 GB of it simulator builds and 0.8 GB updater downloads.
• 1.8–1.9 GB of downloaded Codex updates, cleared on 5 and 11 September.
• 1.6 GB of Codex runtimes cleared on 5 September — and back to 1.6 GB by the 15th.
• 1.4 GB for the ChatGPT app itself, flagged as not opened recently.

That last-but-one line is the pattern: this data regrows, so clearing it once is not the end of it.

Measured again, 1 October 2026

The same Mac, read again to see what had come back:

• Codex runtimes: 1.56 GB — the size it was before the 5 September clear, as it was again on the 15th. Whatever is removed is downloaded again the next time the tool runs code.
• Codex history: 2.94 GB, up from 1.6 GB on 5 September. Nearly double in under four weeks, and none of it is cache.
• Claude Code history and settings: 1.73 GB in ~/.claude.
• Claude desktop caches: 0.99 GB, regrowing after the 4.5 GB clear.

So the caches refill within days and the histories grow without limit. The two need different handling: the first a regular clean, the second a decision about how much history you want to keep, and a copy elsewhere before you trim it.

Where to look

These are the default locations. Size them before deciding anything:

du -sh ~/Library/Application\ Support/Claude/{Cache,Code\ Cache,GPUCache} 2>/dev/null
du -sh ~/Library/Caches/com.openai.* ~/Library/Caches/com.anthropic.* 2>/dev/null
du -sh ~/.cache/* ~/.codex ~/.claude ~/.ollama 2>/dev/null
du -sh /private/tmp/claude-* 2>/dev/null

• App caches — the Cache, Code Cache and GPUCache folders inside an AI app's Application Support folder, and its folder in ~/Library/Caches. Web cache and update downloads.
• Coding agent scratch space — Claude Code works in /private/tmp/claude- followed by your user number. Mostly build output, but not always: an agent can leave a file there that exists nowhere else.
• Runtimes — Codex keeps the runtimes it downloads to run code in ~/.cache/codex-runtimes.
• History and settings — ~/.codex and ~/.claude hold sessions, transcripts and plugins.
• Local models — tools that run models on your Mac, such as Ollama, keep them in folders like ~/.ollama, and many tools cache downloaded models under ~/.cache.

What is safe to delete

• Caches and update downloads: yes. Quit the app first. Conversations stored in your account are on the provider's servers, not in these folders.
• Runtimes: yes, at the cost of a re-download the next time the tool needs one.
• Old agent scratch folders: usually. Skip anything touched in the last hour, which may belong to a session still running, and glance inside before deleting the rest.
• History: only on purpose. ~/.codex and ~/.claude are records, not caches. Move them to the Trash rather than deleting outright, so they can come back.
• Models: only ones you are finished with. They are not corrupted by deleting, but they can be many gigabytes to download again. Use the tool's own remove command where it has one.
• The app you stopped using: uninstall it. That takes its support folder with it, which dragging it to the Trash does not.

Where the app comes in

RefreshYourMac has a section for AI tools. Codex updates and runtimes are rated Safe to Remove; Claude desktop caches and Claude Code scratch folders are rated Review, with any item that may not be regenerable marked and recently used folders left alone; Codex history is rated Move to Backup and goes to the Trash, not oblivion. Apps you have not opened for a while show up in Unused Applications, largest first. It is all measured before anything is offered, and the same scan covers caches and the rest of System Data.