Is it safe to delete cache files on a Mac?

Short answer: user caches are generally safe to delete. Apps store them to start faster and re-create them when they're missing. But "generally" is doing some work in that sentence — clearing caches costs you speed for a while, can sign you out of apps, and some folders that look like caches aren't. Here's how to do it properly.

What a cache is

A cache is data an app can rebuild: thumbnails, downloaded web pages, compiled shaders, previews of your photos. Keeping it saves the app from doing that work again. Deleting it frees space, and the app quietly rebuilds what it needs the next time you use it.

Safe to clear

• ~/Library/Caches — your user caches. Clear the contents of individual app folders, with the app quit.
• Sandboxed app caches — ~/Library/Containers/app/Data/Library/Caches, the same thing for App Store apps.
• Browser caches — better cleared from the browser's own settings (Safari: Settings › Advanced › Show features for web developers, then Develop › Empty Caches; Chrome: Settings › Privacy › Delete browsing data › Cached images and files).
• Logs — ~/Library/Logs for your account; /Library/Logs and /var/log for the system (these need an admin password). Old logs are only useful for troubleshooting.
• Developer caches — Xcode DerivedData, ~/.npm, ~/.gradle/caches, Homebrew's cache (brew cleanup). See deleting Xcode junk.

Be careful with

• Caches of apps that are running. Quit the app first, or it may crash or immediately write the files back.
• Large creative-app caches (Lightroom previews, Final Cut render files). They're safe to delete but can take hours to rebuild. Use the app's own "purge cache" option where it has one.
• The Spotlight index. Deleting it forces macOS to re-index your whole disk, which slows your Mac for a few hours. Only do it if search is broken.

Don't delete

• /System/Library/Caches — protected by macOS, and not yours to manage.
• /private/var/folders — per-user temporary and cache folders macOS manages itself. Clear it by restarting, not by hand.
• ~/Library/Application Support — despite the name, many apps keep real data here (databases, settings, offline files).
• ~/Library/Preferences — deleting these resets apps to their defaults and can lose settings and licence information.

How to clear caches by hand

1. Quit the apps whose caches you'll clear.
2. In Finder, press ⇧⌘G and go to ~/Library/Caches.
3. Switch to list view, turn on Calculate all sizes in View Options, and sort by size.
4. Open the biggest folders and move their contents — not the folders — to the Trash.
5. Restart your Mac, then empty the Trash once everything works as expected.

Waiting to empty the Trash until after a restart gives you an easy undo if an app misbehaves.

Let SpaceSweep pick the safe ones

SpaceSweep separates safe categories from risky ones. Caches, logs and the Spotlight index sit in an Advanced section that stays locked until you confirm you understand the trade-offs.

See SpaceSweep