To clear the cache on a Mac, quit your apps, choose Go › Go to Folder… (⇧⌘G) in Finder, type ~/Library/Caches and move the folders of apps you recognize to the Trash. Leave folders starting with com.apple alone. Clear browser caches from the browser itself. Free Up Space in MrFixable clears app caches in one step.

A cache is a store of files an app saves so it can work faster next time: thumbnails, downloaded images, web pages, data it fetched before. Apps make these files again when they need them, so clearing a cache is safe. It frees space and can fix an app that shows old content or misbehaves. The catch: caches grow back, and an app may be a little slower the first time you open it after clearing.

How do I clear app caches on a Mac?

Quit your apps, open ~/Library/Caches with Finder's Go to Folder command and move the folders of apps you recognize to the Trash. The Caches folder is inside the hidden Library folder in your home folder. Leave the Caches folder itself and anything starting with com.apple in place, then empty the Trash.

Quit the apps whose caches you want to clear. An app that's open can recreate files while you delete them, or misbehave.
In Finder, choose Go › Go to Folder… or press ⇧⌘G (Shift-Command-G).
Type ~/Library/Caches and press Return.
Choose View › as List and View › Show View Options (⌘J), tick Calculate all sizes, then click the Size column to see the biggest folders first.
Select the folders of apps you recognize and choose File › Move to Trash (⌘⌫). Folders are often named like com.developer.appname.
Choose Finder › Empty Trash, then restart your Mac.

Delete the folders inside Caches, never the Caches folder itself. Skip folders whose names start with com.apple: macOS manages those itself.

How do I clear the cache in Safari?

Turn on Safari's developer features, then choose Develop › Empty Caches (⌥⌘E). This clears Safari's stored copies of web pages and images but keeps your history, cookies and logins. Clearing your history instead also removes cookies, which signs you out of websites, so use Empty Caches when you only want the cache gone.

In Safari, choose Safari › Settings, click Advanced and select Show features for web developers.
Choose Develop › Empty Caches (⌥⌘E).

To clear everything for every website, use History › Clear History instead.

How do I clear the cache in Chrome?

Open Chrome's Delete browsing data window from the ⋮ menu, tick only Cached images and files and click Delete data. Leaving cookies unticked keeps you signed in to websites. Choose All time as the time range to clear the whole cache, or a shorter range if only a recent problem needs fixing.

In Chrome, click the ⋮ menu at the top right and choose Delete browsing data.
Choose a time range, such as All time.
Tick Cached images and files and untick the rest if you want to stay signed in to sites.
Click Delete data.

Other browsers have the same option in their settings, usually under Privacy.

What cache files should I not delete?

Don't delete system caches, the Caches folder itself, or anything outside a Caches folder. macOS manages its own caches, and folders like Application Support hold real data and settings rather than temporary files. Leave these places alone, even when a guide online suggests otherwise:

/System/Library/Caches: part of macOS, which protects it anyway.
/Library/Caches at the top level of your disk: shared by every user and by system services.
Folders in ~/Library/Caches whose names start with com.apple.
Anything outside a Caches folder. Application Support, Containers and Preferences hold real data and settings, not caches.

Also be careful with tools that keep more than cache in their cache folders. Some developer tools store downloaded browsers, local history or project indexes there that take a long time to get back.

Clear app and developer caches in one step

Free Up Space in MrFixable lists the caches that are safe to clear, with their sizes, and names the biggest app caches so you can see where the space went:

App caches in your Library folder. Apple's own caches and the caches of apps that are open are skipped, and it checks again just before cleaning, in case you opened an app in the meantime. Caches that hold more than cache, like downloaded test browsers and code editors' local history, are kept.
Xcode build files, old iPhone and Watch debug files, the npm download cache and the Gradle cache, if you have them. The newest debug files for each kind of device are kept.
Downloads older than 30 days and the Trash are listed too, unticked to begin with.

Tick what to clean and click Free Up Space. Caches are deleted for good rather than moved to the Trash, because apps make them again when they need them. MrFixable then tells you how much space was freed.

Browser caches such as Safari's and Chrome's are best cleared from the browser itself, as above.

Questions

Is it safe to clear the cache on a Mac?

Yes, for app and browser caches. They hold temporary copies that apps make again when needed, so clearing them doesn't delete your documents or settings. Quit apps first, and leave folders starting with com.apple and the system's own cache folders alone. An app may open a little slower the first time afterwards.

Will clearing the cache delete my passwords or files?

No. Clearing caches removes temporary copies only, not your documents, photos or passwords. In a browser, clearing only the cache keeps you signed in. Clearing cookies or history as well signs you out of websites, so in Chrome tick only Cached images and files if you want to stay signed in.

How do I clean Mac System Data?

Clearing caches is the safest way to shrink System Data, because caches are part of it. Restart your Mac to clear temporary files, then clear app caches in ~/Library/Caches and empty the Trash. System Data can't be deleted as a whole. See how to clear System Data on a Mac.

How often should I clear the cache on my Mac?

Only when you need the space or an app misbehaves. Caches make apps faster, and they grow back after you clear them, so clearing them every day gains nothing. Checking once every month or two, or when your Mac warns that storage is low, is plenty for most people.

How to clear the cache on a Mac safely