What happens when you clear an app’s cache or data

Two buttons, two very different jobs

On Android, open any app’s storage settings and you find two buttons next to each other: Clear cache and Clear storage (or Clear data). They look like siblings. They are not.

From the developer’s side, an app keeps two kinds of things on your phone.

• Cache. Copies of things it can fetch again: images, previews, bits of web pages. Kept so the app feels fast.
• Data. Everything else: your sign-in, settings, downloads, and anything the app saves only on the phone.

Clear cache throws away the first pile. Clear data throws away both.

What each button deletes

	Clear cache	Clear data
Temporary images and files	Deleted	Deleted
Your sign-in	Kept	Deleted, you sign in again
App settings	Kept	Reset to defaults
Downloads, offline files	Usually kept	Deleted
Things stored only on the phone	Kept	Deleted for good
Your account on the server	Untouched	Untouched

That last row matters. Neither button touches your account. Your email is still on the email provider’s servers, your playlists still on Spotify’s. Only the phone’s copy is affected.

Which one to press first

When an app is slow, shows old content or acts strangely, I would start with Clear cache. It fixes a surprising number of glitches, because a corrupt or stale temporary file is a common cause, and it costs you nothing.

Only if that fails would I move to Clear data. Before pressing it, ask one question: is anything in this app stored only on this phone? If the answer is “I don’t know”, find out first.

The dangerous case: messaging apps

Some apps keep their most valuable content on the device. Chat apps are the classic example. Depending on the app and your settings, your message history may only exist on the phone and in whatever backup you set up.

Clear data on one of those without a recent backup, and the chats can be gone. Cloud-based messengers that keep chats on their servers bring everything back when you sign in. Check which kind you have before you touch the button.

What about iPhone?

iPhone does not give most apps a clear cache button in Settings. The closest tools are:

• Offload App, which removes the app but keeps its documents and data, so reinstalling picks up where you left off.
• Delete App, which removes the app and its data, the same as clear data plus uninstalling.

Some apps have their own clear cache option inside their settings, which is the safest route when it exists.

The short rule

Clear cache freely, clear data carefully. The first is a refresh. The second is a reset, and a reset is only harmless when everything important lives somewhere other than the phone.