App Caches, Cookies, and Local Storage: The Data Your Apps Keep on Your Device
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Apps store more on your device than you might expect. Here's a plain-language guide to the different types of local data and why they exist.
What 'Local Data' Actually Means
When you open an app, it doesn't start from scratch every time. Behind the scenes, apps write small packages of data to your device's storage to make future interactions faster, remember your preferences, or hold session information. This local data takes several distinct forms — and understanding the differences helps you make smarter decisions about storage, privacy, and performance.
| Types of local app data | Cache, cookies, local storage, session storage |
| Cache safety to clear | Yes — no account data or preferences lost |
| Cookie expiry | Set by the issuer; session cookies expire on tab close |
| Local storage expiry | None — persists until manually cleared or app uninstalled |
| iOS native equivalent | UserDefaults and sandboxed file container |
| Android native equivalent | SharedPreferences and internal app directories |
For a broader look at how on-device storage compares to cloud-based options, see our guide to cloud storage vs. local storage trade-offs.
The Three Core Types of Local App Data
App Cache
A cache is a collection of files an app stores so it doesn't have to re-download or reprocess them. A streaming app caches album artwork; a map app caches recently viewed tile images; a browser caches page scripts and stylesheets. The cache is designed to be disposable — clearing it won't log you out or delete your account data, though the app may load more slowly on its next launch while it rebuilds.
Cookies
Cookies are small text files, most commonly associated with web browsers and web-based apps. They store state information: whether you're logged in, what region you selected, or items in a shopping cart. First-party cookies (set by the site you're visiting) and third-party cookies (set by external services embedded in the site) serve very different purposes. Third-party cookies are increasingly restricted by modern browsers due to privacy concerns around cross-site tracking.
Local Storage and Session Storage
Local storage is a web API that allows browser-based apps and progressive web apps (PWAs) to store structured key-value data directly on your device — with no expiration date unless explicitly cleared. Session storage works identically, but is wiped when you close the browser tab. Native mobile apps use equivalent mechanisms: on iOS, UserDefaults and the app's sandboxed file container; on Android, SharedPreferences and internal app directories.
App Cache
Temporary files stored by an app to avoid re-downloading or reprocessing data. Caches speed up load times but can grow large and are safe to clear without losing account data.
Cookie
A small text file placed on your device by a website or web-based app to remember state information such as login sessions or user preferences. Third-party cookies are set by services other than the site you're visiting.
Local Storage
A browser or app mechanism that saves key-value data on your device with no automatic expiration. Unlike cookies, local storage is not transmitted to servers with each request.
Session Storage
Functionally similar to local storage, but data is cleared automatically when the browser tab or session is closed.
UserDefaults (iOS)
Apple's built-in system for native iOS apps to store small amounts of persistent data, such as user preferences and settings, within an app's sandbox.
SharedPreferences (Android)
Android's equivalent to iOS UserDefaults — a lightweight XML-based store for key-value pairs used to persist simple app settings and state.
Why This Matters for Storage and Performance
Caches in particular can grow large over time. A navigation app used frequently might accumulate hundreds of megabytes of map tiles. A social media app stores images and video previews. On devices with limited storage, this accumulation can create real pressure. As storage fills toward capacity, read/write performance degrades — a relationship explained in more depth in our article on storage capacity and app performance.
~500 MB
Typical cache size for a heavy-use navigation app
Map tile caches for frequently used navigation apps can exceed 500 MB depending on regions saved and usage frequency.
5 MB
Default local storage limit per origin in most browsers
Most major browsers cap web local storage at around 5 MB per origin by default, though some allow more with user permission.
On Android, you can inspect per-app storage usage under Settings > Apps > > Storage, which separates app data from cache. On iOS, go to Settings > General > iPhone Storage for a breakdown. Both platforms allow cache-clearing on a per-app basis without affecting your account or saved preferences.
It's also worth understanding how background activity interacts with local data. Apps that refresh content in the background continuously write to their caches — see our overview of background app activity for details on managing this behavior.
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Apps & Software Editorial Team
Apps & Software Editorial Team is the collective byline for our editorial team and contributor network. Articles published under this byline or an editorial pen name are researched, written, and reviewed according to our editorial standards for clarity, consistency, and independence before publication.
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