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What Is an SD Card Reader?

By Felicia Dye
Updated May 16, 2024
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SD cards are small storage devices that are used to supply or increase the memory capacity of another device. An SD card reader is a device that allows the files on an SD memory card to be accessed. This type of reader can be an external accessory, or it can be built into a larger device.

An SD card can be used with a variety of devices, such as cell phones, computers, and digital cameras. If a person has an SD card reader, she can access the files that she stored without the original device that was used to create them. The card reader can, therefore, act as a medium when a person wants to copy or transfer files from one device to another.

An external SD card reader is generally a basic device. Most are lightweight and compact. To use it, a person simply inserts the SD card into the provided slot; some models require the SD card to be inserted upside down. The device can then be connected to another device, such as a laptop, where the files can be accessed.

The most common way to connect an SD card reader to a computer or other device is by using a USB plug. FireWire or parallel printer ports may also be used. The cord that is used to connect the device to another may or may not be detachable.

Every SD card reader will not produce the same results. Speed is one feature that can differ amongst them. Speed in this sense refers to how long it will take for the information from the memory card to be accessed by the other device. Some do not read the data from the memory cards as quickly as others. Another major difference is that some readers may not read certain cards at all.

SD cards not only come with different storage capacities, they also come in different sizes and shapes. Individuals who have several different sizes of SD cards may want to consider a multi SD card reader. These devices generally have several slots, which allows one device to be used to read several types of SD cards.

An SD card reader is not always an external device. Many devices, including some computers and printers, have built in readers. These work on the same premise as the external devices. One disadvantage, however, is that when the SD reader is built in, it may not be able to read memory cards of varying sizes.

What Does an SD Card Do?

An SD (Standard Digital) card is a storage medium for digital files like photos, songs, or word processing documents. Remember floppy disks? SD cards are their younger, cooler cousins. They may be tiny, but don’t let their small stature fool you. SD cards can pack a big punch when it comes to storage. They’re available in various storage size capacities. Depending on the card type, they can store anywhere from 2 GB to 1 TB of digital data. In real-world applications, 1 GB can hold nearly 600 photos, while 1TB could hold up to 250,000. It’s important to note that while they are available, 1 TB cards aren’t the norm. Everyday users typically stay within the 2 GB to 64 GB range.

What Are Other Storage Mediums?

SD cards aren’t the only option for digital storage. Many devices are compatible with other storage devices. USB drives or external hard drives are all capable of holding digital data. Each of these tools has its niche in the realm of information storage.

Comparing SD, USB and External Hard Drives

SD cards are ideal for expanding the memory of a device. For example, video game consoles often include SD card slots to download games. The added memory allows the user to free up space on the game console. Having extra storage space in an SD card often enables faster device performance. You can also use them to transfer data from one device to another.

USB drives offer similar storage to an SD card. They are often compatible with computers and laptops, so they’re great for transferring files. They’re sometimes a little easier to keep track of due to their larger size. Many people keep USB sticks attached to lanyards for easy access during the workday. USB drives stick out of devices, so they aren’t ideal for keeping installed around the clock. They’re also easily damaged, leading to data loss or corruption.

External hard drives offer large storage capacities and are best for long-term use. Hard drives don’t run on flash memory like the other options listed, so they tend to be more stable. The primary benefit of external hard drives is to extend a computer’s storage space.

How do SD Cards Work?

Many gadgets today are compatible with SD cards. Here are just a few products that are compatible with external digital storage.

  • Computers
  • Cell Phones
  • Digital or Video Cameras
  • Surveillance Cameras
  • Video Game Consoles
  • Medical Devices
  • Digital Music Players

Files are stored on an SD card using flash memory chips embedded within the card. This non-volatile storage medium can hold information without supplying power to the chip. This feature lets you safely take the SD card in and out of your device without losing data.

SD cards usually remain in a device, like a camera, until you’re ready to view the captured data. Be sure to read your device’s instruction manual regarding storage cards. Some will automatically delete the oldest information on a card when the storage is full. It’s crucial to periodically upload the data to your computer to avoid losing any data. Consider keeping a spare SD card on hand to replace full cards quickly.

How to Use SD Card Reader

These days, most computers come standard with SD card readers. SD card readers allow you to view and transfer files stored on the card. If your computer doesn’t have one, you may be able to attach an external SD card reader.

Transferring these files to your computer is simple. First, you’ll need to take the card out of the device where it collected data. SD card slots use a “push/push mechanism” to insert and release cards. Push in on the card to remove it from your device. You will feel it discharge, then pop itself out of the device. Next, insert the card into your computer’s SD card slot the same way. If you’ve correctly installed it, you’ll hear an audible click.

Wait a moment while your computer recognizes the new card you’ve just installed. Then, open your “files” folder. You should now see the name of your SD card in the file options. Open that folder to view your data. It’s not enough to view the files if you want to save them. You also need to upload them to your computer. Select each file you want to keep and save them to the preferred location on your computer. At this point, you can delete these files from your SD card to free up space. Utilizing an SD card reader is an easy way to improve the performance of your electronic device.

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Discussion Comments
By anon303694 — On Nov 15, 2012

I am so confused! Help! When I insert my micro SD card into my newly bought card reader and put it into my laptop, then it says i have to format it. Doesn't this then mean that I will lose everything on my SD card?

By jmc88 — On May 30, 2012

I saw an interesting product the other day that was a combination of an SD card reader than a USB device. It could hold flash memory like a USB drive but also had a place to insert an SD card.

I think that would be really handy if you had something where you needed to carry around a lot of different information for an SD card. If you were using the SD card for data storage, you could dump the information onto the USB drive if you had to.

It would also be more useful for connecting the SD card to a computer that didn't have the card readers. I don't think it was very expensive, either. It just seems like something that might be a good gift for a photographer or a student who needs to use SD cards for something.

By cardsfan27 — On May 29, 2012

I was not aware that certain SD card readers worked at different speeds. Maybe that is what is causing my problem.

I bought a general card reader the other day, and it has trouble working on my computer. I have several different cameras, and it seems like each of them takes a different type of card. The card readers on computers usually don't take the larger type of card, either.

Anyway, whenever I hook the thing up through a USB port, it takes a long time to connect to the computer. Whenever I try to copy the pictures from the card reader to the computer, it takes a lot longer than I think it should. I just bought the cheapest card reader they had, so I bet that's the problem. I guess maybe I'll look into buying a better one.

By TreeMan — On May 28, 2012

@Izzy78 - In order to get a micro SD card to work with a computer you need to have a special adapter. Typically, when you buy the cards at the store, they will come with the adapter, but if you bought the GPS unit from someone else, it sounds like they didn't include the adapter.

I've never had to buy one myself, but I would assume you can find the adapters by themselves. I would check a store like Best Buy. If they don't have them, I'm sure you could find one online.

Given how inexpensive SD cards are, it might just be simpler to buy a brand new card. For a GPS, it is doubtful that you need more than a 4GB SD card and reader, which shouldn't cost more than $15 if even that. That way you'll also have two cards, and you can store different maps if you need them.

By Izzy78 — On May 27, 2012

This may be a silly question, but how do I use a computer to read a micro SD card? I bought a handheld GPS unit from someone, and it came with a micro SD card that holds all of the maps and different data on the unit. I would like to install new maps for where I live, but I don't know how to access the information on the card.

I have a desktop and laptop computer that each have the special ports where you can put in several different types of cards. These spots are all too large for the card I have.

If you aren't familiar with a micro SD card, they are just about half an inch long and very thin. I looked at USB SD card readers, but they didn't look right, either.

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