Quick fix: For full-size SD cards, flip the physical lock switch up (toward the contacts). For micro-SD-in-adapter, the switch is on the adapter — flip it. If no physical switch or switch is already up, run diskpart → select disk N → attributes disk clear readonly.

You plug an SD card into your reader and Windows says the card is write-protected. You can read files but not modify or delete. Full-size SD cards have a physical write-protect switch on their left edge — easy to bump into the wrong position. Micro SD cards in an adapter have the switch on the adapter. And if no physical switch is set, Windows’ own read-only attribute may be the cause.

Symptom: SD card or micro-SD-in-adapter reports as write-protected; cannot write, delete, or format.
Affects: Windows 11 (and Windows 10) with SD card readers.
Fix time: ~5 minutes.

What causes this

Three write-protection sources: Physical switch — full-size SD and SDHC/SDXC cards have a small slider; if positioned toward the bottom of the card, write is blocked. Windows read-only attribute — a system-side flag stored in the disk’s metadata, sometimes set by accident or by tools like ImageWriter. Card firmware lockup — failing or worn-out cards enter permanent read-only mode at the controller level to protect data.

Method 1: Check the physical write-protect switch

Always check first. This is the cause in most reported “SD card write-protected” cases.

Eject the SD card from Windows: right-click in File Explorer → Eject.
Pull the SD card out of the reader.
Look at the left edge (when the card is oriented with contacts facing you). There’s a small switch about halfway down.
If the switch is positioned toward the bottom edge (away from contacts), the card is locked. Slide it up toward the contacts to unlock.
If the switch is loose or broken (a common failure on cards that have been re-locked many times), use a small piece of tape to hold it in the unlocked position.
For micro-SD cards in SD adapters: the switch is on the adapter, not the micro-SD itself. Check the adapter’s switch.
Reinsert the card. Try writing.

If the switch was the cause, write works immediately. If the switch is already up and write still fails, proceed to Method 2.

Method 2: Clear Windows read-only attribute with diskpart

Use when physical switch is correct but write-protection persists.

Plug in the SD card.
Open Terminal (Admin).
Launch diskpart:
```
diskpart
```
List disks:
```
list disk
```
Identify the SD card by size — e.g., a 64 GB card shows as ~58 GB.
Select it (replace N with the disk number):
```
select disk N
```
Be very careful — selecting the wrong disk could affect a different drive.
Check current attributes:
```
attributes disk
```
Look for Read-only: Yes.
Clear read-only:
```
attributes disk clear readonly
```
Verify:
```
attributes disk
```
Should show Read-only: No.
Exit and try writing.

This catches Windows-side write protection.

Method 3: Format the card (last resort if data is backed up)

Use when Methods 1 and 2 don’t restore write capability — typically because the filesystem itself is corrupted.

Important: this destroys all data on the card. Copy off anything important first.
Open Terminal (Admin).
Use diskpart to format:
```
diskpart
list disk
select disk N
clean
create partition primary
format fs=exfat quick label="SDCARD"
assign
exit
```
For cards 32 GB or smaller, use fs=fat32 for broader compatibility (cameras, dashcams). For larger cards, exFAT is correct.
The card now has a fresh filesystem and full write capability.

If formatting also fails with write-protection error, the card has likely entered hardware-level read-only mode — the controller has detected too many failed writes and is preserving what data remains. The card is failing; copy your data off and replace the card.

How to verify the fix worked

Try to create a new file on the card via File Explorer — it should succeed.
Copy a test file to the card. Copy completes without errors.
Right-click the SD card in File Explorer → Properties. The card’s Used space should reflect newly-written data.
Run fsutil fsinfo volumeinfo F: (replace F: with the SD card’s letter) in Terminal — confirms filesystem is writable.

If none of these work

If the SD card remains write-protected after physical switch, diskpart, and reformat attempts, the card itself is failing. Wear leveling exhaustion: SD cards have a finite number of write cycles per NAND cell. When the controller exhausts spare blocks, it enters permanent read-only mode to preserve existing data. No software fix exists. Copy the data off and replace the card. Card reader issue: occasionally the reader, not the card, is the cause. Try the card in a different reader (USB SD reader, a different laptop’s built-in reader, a camera) — if it works elsewhere, the reader is at fault. Counterfeit card: cheap SD cards from unreliable sources sometimes report fake capacity. Test with H2testw (free) — if real capacity doesn’t match advertised, the write protection is the controller’s defensive flag. Return for refund if possible.

Bottom line: Most SD card write protection is the tiny physical switch — check that first. Diskpart handles Windows-side flags. Persistent write protection on a healthy card with switch up usually means the card is failing.