What is an SD Card Reader?

Felicia Dye

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.

A SD card.
A SD card.

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.

SD cards can be used to store photos and video taken on digital cameras.
SD cards can be used to store photos and video taken on digital cameras.

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.

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Discussion Comments


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?


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.


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.


@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.


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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