What Does the Lock on an SD Card Do & When to Use It?

The short answer is:

When activated, the lock on the side of an SD card places the card into “read-only” mode. This prevents files from being edited or deleted and also disables the creation of new files. You might want to lock your SD card when accidental deletion is a concern.

You can slide the switch up or down to unlock or lock the SD card.

I’m Caleb, and I have five years of experience using SD cards regularly as a photographer. They’ve been my main go-to for getting pictures from my camera to other devices.

In this article, I’ll explain the lock on the side of an SD card. I’ll also go into the times it could be useful to you. If you’ve ever seen this feature and aren’t sure what it’s for, keep reading for the full explanation.

What Does the Lock on an SD Card Do?

On the side of your SD card, you might find a switch with a label like “LOCK.” The purpose of this switch is‌ pretty simple. If you move the switch into the lock position, it will place the card in read-only mode.

With your SD card in read-only mode, you can view the files on the card but not edit or delete them. You also won’t be able to create new files.

So, if you’re confused by why you can’t edit or delete any files on your SD card or move new files to the card, you should check the lock setting. Odds are, you might have locked the card and enabled read-only mode without realizing it.

When to Lock an SD Card

The main point of locking an SD card is to avoid accidental file deletion. For example, let’s say you’ve backed up many of your photos on an SD card while you wait to move them to another device.

If you lock the card in this situation, you don’t have to worry about pressing the wrong button and losing your valuable files when transferring.

Maybe you’re using the locked card with a device like a camera, and you inadvertently selected an option to format the SD card without getting your files off it first. 

Even in this extreme scenario, your files would be safe, as the lock would prevent any files from being deleted or altered.


These are some of the most common questions about locking SD cards.

Why Does an SD Card Have a Lock?

SD cards have locks as an extra layer of protection for the user’s data, as they can prevent files from being accidentally deleted or changed.

Should an SD Card Be Locked or Unlocked?

If you’re actively adding files to an SD card or modifying the files on one, you must keep it unlocked. However, if you want to make sure the files stay as they are, locking the card is a good idea.

How Can I Change My SD Card From Read Only to Normal?

Check to see if the switch on the side of the SD card is in the lock position. If it is, simply slide the switch in the opposite direction.

Will an SD Card Take Pictures If It Is Locked?

No, an SD card won’t accept new pictures if it’s in locked mode. Locking an SD card prevents further data from being written, which includes image files.


The lock on an SD card activates read-only mode, which prevents the files on that card from being altered or deleted. It also keeps new data from getting written. You may want to lock your SD card if you need to make sure the contents of the card stay the same.

Have you ever accidentally deleted files thanks to not knowing about this feature? Let us know in the comments!

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  • Ezequiel M

    Thank you for the straight-forward and simple answer. I’ve been wondering about this for a while now, so it’s good to finally have an answer.