Fix Corrupt SD Card on Android — Repair, Recover & Prevent Data Loss

Signs Your SD Card Is Corrupt

SD card corruption doesn't always announce itself clearly. Here are the symptoms, from subtle to obvious:

Early warning signs:

• Some files take unusually long to open
• Thumbnails don't load for some photos/videos
• A few files show as 0 KB size
• Occasional "file not found" errors for files you know exist

Clear corruption indicators:

• Android notification: "SD card is damaged. You may have to reformat it"
• Card appears empty despite having data
• Phone asks to format the card every time you insert it
• Files appear with garbled names (random characters)
• Apps that store data on SD card crash on launch

Severe corruption:

• SD card not detected at all (doesn't appear in Settings → Storage)
• Phone freezes when you try to access the card
• "Read-only file system" error when trying to write

Step 1: Unmount and Remount (Fixes Minor Issues)

The simplest fix that resolves many temporary corruption issues:

1. Settings → Storage → SD card → Unmount (or Eject)
2. Wait 10 seconds
3. Tap Mount (or remove and reinsert the card)
4. Check if files are accessible again

Why this works: Android's file system cache can become inconsistent. Unmounting forces the system to flush all pending writes and re-read the card's file allocation table from scratch.

Step 2: Restart Your Phone

A full restart resets the SD card controller hardware:

1. Power off completely (not just sleep)
2. Wait 30 seconds
3. Power on
4. Check SD card access

Why this works: The SD card controller chip can enter an error state that persists through soft reboots. A full power cycle resets it.

Step 3: Save Accessible Files First

Before attempting any repair that might make things worse, copy what you can:

1. Open AnExplorer → navigate to SD card
2. Browse folders — some files may still be readable even if others aren't
3. Copy accessible photos, videos, and documents to:
   • Internal storage (if you have space)
   • Cloud storage (Google Drive, MEGA, Dropbox)
   • NAS via SMB (if available)
   • PC via Device Connect

Priority order for saving:

1. Photos/videos in DCIM (irreplaceable memories)
2. Documents and downloads (may be re-downloadable but save anyway)
3. App data (game saves, WhatsApp backups)
4. Music (usually re-downloadable)

Step 4: Repair on PC (chkdsk / fsck)

If the card is partially readable but has errors, a PC can often repair the file system:

Windows:

1. Remove SD card from phone → insert into PC (use a USB card reader)
2. Open Command Prompt as Administrator
3. Type: chkdsk E: /f (replace E: with your card's drive letter)
4. Wait for scan and repair to complete
5. Safely eject → reinsert into phone

Mac:

1. Insert SD card into Mac (use card reader)
2. Open Disk Utility (Applications → Utilities)
3. Select the SD card → click "First Aid" → Run
4. Wait for repair → eject → reinsert into phone

Linux:

1. Insert card → identify device (lsblk)
2. Run: sudo fsck.vfat -a /dev/sdX1 (for FAT32) or sudo fsck.exfat /dev/sdX1 (for exFAT)
3. Eject → reinsert into phone

What chkdsk/fsck fixes:

• Cross-linked files (two files claiming the same disk space)
• Lost clusters (allocated space not belonging to any file)
• Invalid file entries in the directory table
• Incorrect file sizes

Step 5: Format as Last Resort

If the card is unreadable or repair fails, formatting is the nuclear option:

On Android:

1. Settings → Storage → SD card → Format (or Format as portable/internal)
2. Choose "Portable storage" (recommended — works in multiple devices)
3. Confirm — all data is erased, file system is rebuilt fresh

On PC (recommended for better formatting options):

1. Insert card into PC
2. Windows: Right-click drive → Format → choose exFAT (64+ GB) or FAT32 (32 GB or less)
3. Mac: Disk Utility → Erase → choose ExFAT
4. Full format (not quick) is recommended for cards with suspected hardware issues

After formatting: The card works like new. Reinstall apps that used SD storage, and restore backed-up files.

Preventing Future Corruption

Always unmount before removing: Settings → Storage → SD card → Unmount before physically removing the card. Pulling it out while the system is writing causes corruption.

Don't use the card in multiple devices: Each device formats the card slightly differently. Switching between phone, camera, and PC increases corruption risk. Dedicate cards to one device.

Buy quality cards (avoid counterfeits): Counterfeit SD cards (common on Amazon/AliExpress) have fake capacity and poor controllers. Buy from authorized retailers. Samsung EVO, SanDisk Extreme, and Kingston Canvas are reliable brands.

Avoid filling the card completely: Leave 10-15% free space. A completely full card has no room for file system metadata updates, increasing corruption risk.

Don't remove during transfers: If AnExplorer is copying files to/from the SD card, wait for the operation to complete before unmounting or removing.

Replace aging cards: SD cards have a limited number of write cycles (typically 10,000-100,000 depending on quality). If a card is 3-5 years old and corrupts frequently, it's worn out — replace it.

When the Card Is Physically Dead

If no device (phone, PC, camera) can detect the card at all:

• The card's controller chip has failed — no software fix exists
• Professional data recovery services can sometimes read the NAND flash directly ($100-500+)
• For irreplaceable data (wedding photos, etc.), professional recovery may be worth the cost
• For replaceable data, accept the loss and buy a new card

Related Guides

• SD Card Not Showing — card not detected at all
• Can't Access USB Drive — USB OTG troubleshooting
• Move Files to SD Card — proper SD card usage
• Android Storage Full — free up space when storage is full