Android File Types Explained — APK, OBB, Cache, Data

APK files are Android app installers (like .exe on Windows), OBB files are game expansion data (maps, textures, audio), cache is temporary data safe to delete anytime, and data files contain your personal settings and saves that reset the app if deleted. Understanding these file types helps you manage storage confidently — knowing what is safe to delete and what to leave alone.

The Main Android File Types

APK — Android Package Kit

What it is: The installation package for Android apps. Every app you install comes from an APK file.

Extension: .apk

Found in:

• /data/app/ — installed app APKs (system-managed, usually hidden)
• Download/ — APKs you manually downloaded
• Various folders — APKs shared via messaging or Bluetooth

Size: 5 MB to 200+ MB per app

Safe to delete?: ✅ Yes — APKs in your Download folder are installers that are no longer needed after the app is installed. Like a setup.exe on Windows after installation. Deleting them does NOT uninstall the app.

What is inside an APK:

• classes.dex — compiled app code
• res/ — images, layouts, strings (app resources)
• lib/ — native code libraries (C/C++ components)
• assets/ — raw files the app needs
• AndroidManifest.xml — app configuration, permissions

OBB — Opaque Binary Blob (Expansion Files)

What it is: Additional data files for large games and apps that exceed the Play Store APK size limit.

Extension: .obb

Found in: Android/obb/[package.name]/

Size: 100 MB to 2+ GB per game

Safe to delete?: ⚠️ Conditionally — if you still play the game, deleting forces a full re-download (which can be 1-20 GB). If you have uninstalled the game and the folder remains, it is safe to delete the leftover OBB folder.

Examples:

• main.123456.com.game.example.obb — primary expansion file
• patch.123457.com.game.example.obb — update/patch expansion file

Games like Genshin Impact, PUBG Mobile, and Call of Duty Mobile use massive OBB files for maps, textures, character models, and audio that do not fit in the base APK.

Cache Files

What it is: Temporary data apps store to speed up future operations. Thumbnails, web page data, prefetched content, and processed results.

Found in:

• Android/data/[package.name]/cache/ — per-app external cache
• /data/data/[package.name]/cache/ — per-app internal cache (hidden without root)

Size: 10 MB to 5 GB per app (social media apps cache aggressively)

Safe to delete?: ✅ Always safe. Cache is explicitly designed to be expendable. Deleting it:

• Does NOT log you out
• Does NOT delete messages or saves
• Does NOT affect app functionality
• May make the app slightly slower on first use (rebuilds cache)

What caches typically contain:

• Image thumbnails (faster gallery browsing)
• Web page data (faster page loads)
• Video previews (social media feeds)
• Map tiles (faster map display)
• Album art (music apps)
• API response data (faster app start)

Data Files

What it is: Your personal data within apps — login credentials, settings, preferences, message databases, game saves, and downloaded content.

Found in:

• Android/data/[package.name]/files/ — per-app external data
• /data/data/[package.name]/ — per-app internal data (hidden without root)

Size: Varies enormously (1 MB for settings to 10+ GB for game saves and offline content)

Safe to delete?: ❌ Usually NOT safe. Deleting data resets the app completely:

• Logs you out of all accounts
• Deletes message history
• Removes game progress and saves
• Clears all preferences and settings
• The app returns to its fresh-install state

Exception: Folders in Android/data/ for apps you have already UNINSTALLED are safe to delete — they are orphaned data with no app to use them.

DEX — Dalvik Executable

What it is: Compiled bytecode that runs on Android's runtime (ART/Dalvik). Think of it as the executable code of Android apps.

Extension: .dex, .odex, .vdex

Found in:

• Inside APK files (classes.dex)
• /data/dalvik-cache/ — optimized versions for faster loading

Safe to delete?: ❌ Never manually delete. Android manages these automatically. If you clear dalvik-cache, the system rebuilds it on next boot (but the boot takes much longer).

.nomedia

What it is: An empty marker file that tells Android's media scanner to skip the containing folder. All media in folders with .nomedia is hidden from gallery apps, music players, and video apps.

Extension: No extension — the filename IS .nomedia

Found in: Various media folders (app asset folders, hidden folders, private content folders)

Size: 0 bytes (empty file)

Safe to delete?: ⚠️ Depends on intent:

• Deleting it makes that folder's media appear in your gallery
• Some apps intentionally use .nomedia (removing it causes app assets to pollute your gallery)
• If YOU placed it to hide private photos — deleting exposes them to gallery

Android's Folder Structure Explained

Root-Level User Folders

The Android/ Folder

The most confusing folder for non-technical users:

Android/
├── data/          ← App-specific storage (caches, saves, configs)
│   ├── com.whatsapp/       ← WhatsApp data
│   ├── com.spotify.music/  ← Spotify data
│   └── com.game.name/      ← Game saves and cache
├── media/         ← App media files (WhatsApp on Android 11+)
│   └── com.whatsapp/       ← WhatsApp media
└── obb/           ← Game expansion files
    └── com.game.name/      ← Large game assets

Android/data/:

• Contains one subfolder per installed app
• Each subfolder has files/ (persistent data) and cache/ (temporary data)
• On Android 13+, this folder is not directly accessible without root
• Folders left behind after uninstalling an app are safe to delete

Android/media/:

• Newer location for app media (Android 11+ migration)
• WhatsApp moved here from the root WhatsApp/ folder
• File managers with All Files Access can browse this

Android/obb/:

• Game expansion files only
• Large binary blobs of game data
• On Android 13+, not directly accessible without root

System-Level Files (For Reference)

These are usually invisible without root access:

Rule: Never delete system files unless you know exactly what you are doing. Modifying /system/ or /data/system/ can brick your device.

What is Safe to Delete — Quick Reference

Always Safe ✅

• APK files in Download (after installation)
• .tmp files anywhere
• .thumbnails folders
• Cache folders for any app
• Android/data/ folders for uninstalled apps
• Android/obb/ folders for uninstalled games
• .DS_Store files (macOS artifacts)
• .Trash/ or .trash/ contents
• .log files in most locations
• Old screenshots you don't need

Usually Safe ⚠️ (Check First)

• OBB files for games you still play (forces re-download)
• WhatsApp media you've already backed up
• Old voice recordings
• Downloaded music you have streaming access to
• Old documents (verify you don't need them)

Never Delete ❌

• Files in /system/ (without root knowledge)
• Active app data (in /data/data/) — resets the app
• .dex / .odex / .vdex files — breaks apps
• Files you don't recognize in system directories
• Databases (.db) without understanding what they store

Identifying Unknown Files

When you find a file and do not know what it is:

1. Check the extension: Look it up if unfamiliar
2. Check the location: Files in app-specific folders belong to that app
3. Check the size: Very large files in unexpected locations may be downloads or caches
4. Check the date: Very old files in temp/cache locations are usually safe to delete
5. When in doubt, leave it: Move it to a "review" folder instead of deleting

Common Mysterious Extensions

Related Guides

• OBB and Data Folders — deep dive into Android/obb and Android/data
• Clear Cache on Android — safe cache cleaning guide
• Storage Full — reclaim space using this knowledge
• Internal vs External Storage — where everything lives physically