Transfer Files from Android to USB Drive (OTG)
USB OTG (On-The-Go) lets your Android phone act as a USB host — you plug in a flash drive or external hard drive and AnExplorer reads it directly. No cloud, no Wi-Fi, no PC. Great for offline backups, sharing files at events, or offloading media from a trip.
What You Need
- Android phone with USB OTG support (most phones from 2014+ support this)
- USB OTG adapter: USB-C to USB-A for newer phones, or Micro-USB to USB-A for older
- USB flash drive or portable hard drive (SSD recommended for speed)
- AnExplorer installed on your phone
Step-by-Step: Copy Files to USB Drive
- Connect the OTG adapter to your phone, then plug in the USB drive
- Android will show a notification: "USB drive detected" — you can dismiss it
- Open AnExplorer — in the left panel, you'll see your USB drive listed (e.g.,
USB Storageor the drive label) - Navigate to the files you want to copy on your phone (e.g.,
/DCIM/Camerafor photos) - Long-press a file or folder to select it → tap More → Copy (or Cut to move)
- Navigate to the USB drive in the left panel
- Tap Paste — AnExplorer copies the file to the drive
Repeat for any folder structure you want to replicate.
Format Compatibility
AnExplorer reads and writes these USB drive formats without root:
| Format | Read | Write | Max File Size | Notes |
|---|---|---|---|---|
| FAT32 | ✅ | ✅ | 4 GB | Most compatible — works on Windows, Mac, TV, PlayStation |
| exFAT | ✅ | ✅ | 16 EB | Best for large files — works on Windows/Mac natively |
| NTFS | ✅ | ✅ | 16 TB | Windows-native — full read/write in AnExplorer |
| ext4 | ✅ | ✅ | 16 TB | Linux format — commonly used for NAS backup drives |
The most important caveat: FAT32 has a 4 GB maximum file size. If you're copying a 4K video larger than 4 GB to a FAT32 drive, the copy will fail. To fix this, reformat the drive to exFAT.
How to Reformat a Drive to exFAT
If you bought a brand-new drive and it's FAT32 (limits you to 4 GB files):
On Windows:
- Insert the drive in your PC → open File Explorer
- Right-click the drive → Format
- File system: exFAT → Start
On Mac:
- Open Disk Utility → select the drive
- Click Erase → Format: exFAT → Erase
On Android with AnExplorer (for small drives only, < 128 GB):
- AnExplorer → USB drive → ⋮ menu → Format
- Select exFAT → Confirm
What Files to Move
Common use cases for phone-to-USB transfer:
| Content | Location on Phone | Notes |
|---|---|---|
| Photos & videos | /DCIM/Camera/ | Camera Roll — often the biggest folder |
| Screenshots | /Pictures/Screenshots/ | |
| Downloads | /Download/ | Documents, PDFs, APKs |
| WhatsApp media | /Android/media/com.whatsapp/WhatsApp/Media/ | Images, voice notes, documents |
| Music | /Music/ | |
| App backups (APK) | /Android/data/<app-pkg>/ | Requires more permissions on Android 11+ |
Copy vs. Move (Cut)
- Copy: Files stay on phone AND appear on USB drive. Use this when you want a backup.
- Move (Cut): Files are deleted from phone after paste completes. Use this to free up phone storage.
Recommendation: Copy first, then verify the files on the USB drive are readable before cutting the originals. AnExplorer shows file sizes after paste — confirm they match.
Speed Tips
USB drives vary enormously in transfer speed:
| Drive Type | Typical Write Speed | Time for 10 GB |
|---|---|---|
| Cheap FAT32 flash drive | 5–10 MB/s | 17–33 min |
| Mid-range USB 3.0 flash | 30–80 MB/s | 2–5 min |
| USB 3.1 SSD | 300–500 MB/s | 20–30 sec |
USB OTG is usually limited to USB 2.0 speeds (up to ~40 MB/s) unless your phone supports USB 3.0 OTG (Pixel 7+, Samsung S21+, OnePlus 9+).
Backup Use Case: Full Phone Backup to USB
Before upgrading your phone or doing a factory reset, you can back up everything manually:
- Create a folder on the USB drive:
Phone Backup YYYY-MM-DD - Copy these folders from your phone:
/DCIM/— all photos and videos/Download/— downloaded files/Pictures/— screenshots, saved images/Music/— local music files/Android/media/com.whatsapp/WhatsApp/— WhatsApp data/Documents/— any local documents
- Keep the USB drive in a safe place until setup is complete on the new phone
For APK backups, see the backup apps to APK guide.
Troubleshooting
"Permission denied" when writing to USB
- Android 12+ requires confirming USB write permissions
- When AnExplorer first detects the USB drive, select Full access (not Read-only) in the system picker dialog
- If you dismissed that dialog: Settings → Apps → AnExplorer → Permissions → Storage → Allow all the time
USB drive not showing in AnExplorer
- Unplug and re-plug the OTG adapter
- Check Android notification drawer — did Android detect the drive?
- Some USB drives draw too much power — try a USB hub with its own power adapter, or use a USB-C SSD instead of a spinning HDD
- Try a different OTG adapter — not all cables pass through the data pins
Copy fails midway on large files
- Check for FAT32 format (4 GB file size limit) — reformat to exFAT
- Ensure the drive has enough free space
- Keep the screen on during transfer — some phones suspend USB OTG when the screen turns off
Phone gets hot or battery drains fast
USB OTG powers the drive from your phone's battery. For a 2.5" spinning hard drive, this can drain the battery quickly. Use an externally-powered USB hub, or prefer a bus-powered SSD.
Related Guides
- Transfer SD Card to Phone — copy from SD card to internal storage
- Copy Files to PC — Windows PC wireless transfer
- Backup Apps to APK — APK backup to USB drive