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What is an SD Card?

SD memory cards are compact, portable memory cards powering the future of the digital world. SD memory cards are like tiny disk drives that enable you to quickly capture and store video, photos, sound and documents in a reliable, easy-to-use format.  SD cards are also an excellent transfer medium for large data collections.

SD technology is the de-facto industry standard for mobile phones, digital cameras, MP3 music players, personal computers, printers, car navigation systems, electronic books, and other consumer electronic devices. SD technology is used in some 400 products across dozens of product categories and in more than 8,000 models.

SD memory cards are available in standard and high-capacity formats along with a variety of speed classes.   In 2009, 76% of cell phones were shipped with microSD cards.

The most flexible way to buy an SD card is as a microSD card in a full-size adapter, so that your card can be read in computers, photos frames, cell phones, and virtually every device that accepts SD cards.

SD Card Devices

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Where can I find the SD Card Reader on my computer?

SD Card Slot on a Laptop ComputerOn a laptop, the SD Card Reader is usually a single slot about an inch wide on the side of the computer.  Desktop or tower computers often have a built-in multi-card reader that accepts SD cards as well as other memory card sizes.  If you do not have a built-in SD Card Reader, you can plug an external SD Card Reader into a USB port.  As of this writing, SD Card Readers are about $20 from online sources.  Be sure that the reader you buy is SDHC compatible so that you can read cards larger than 2GB.  
  External and Internal SD Card Readers  

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How can I tell how fast an SD Card is?Arrow points to Class 4 designation

Slow SD Cards are frustrating and virtually useless for many applications - especially photos, videos and music.  Class 2 cards transfer data at 2MB per second; Class 4 cards transfer data at 4MB per second or faster.  As an example, it would take about a minute to write an 8GB Class 2 card;  a Class 4 card would take about 30 seconds.

Leading SD Card manufacturers advertise the speed on the outisde of the card in a circle (illustrated here.)  However, imported knock-offs also copy this logo;  we have seen cheap imported cards that read and write as slowly as 50K per second instead of the 4MB second advertised.

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What is the largest SD card that I can buy?

As of March 2010, the largest SD card available for purchase is 64 gigabytes (GB) and the largest microSD card is 32GB. The smallest cards generally available are 1GB;  cards smaller than 1GB are available, but at about the same cost.  Beyond capacity, the most important differentiator between SD cards is speed:  your SD card becomes another disk drive, which, if it is too slow, is intolerable.

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How much space is available on an SD Card after formatting?

Like disk drives, SD Cards are formatted, and the formatting takes a small amount of space.
SD Card Size Space Available
After Formatting
1 GB SD Card 965 MB  
2 GB SD Card 1.85 GB  
4 GB SD Card 3.68 GB  
8 GB SD Card 7.40 GB  
16 GB SD Card 14.80 GB  
32 GB SD Card 29.60 GB  
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How should I format my SD Card? 

Why are SD cards often formatted with the FAT filesystem?

The FAT16/FAT32 file system is often used because the ubiquity of this file system allows the card to be accessed on virtually any host device with an SD reader. Also, standard FAT maintenance utilities (e.g. SCANDISK) can be used to repair or retrieve corrupted data. However, because the card appears as a removable hard drive to the host system, the card can be reformatted to any file system supported by the operating system but MAY NOT be recognized by media players or other SD devices.

Can I format my SD card on other file or operating systems?

SD cards can be formatted using, for example, the UUFS, EXT3 or the ReiserFS file systems; under Mac OS X, SD cards can be partitioned as GUID devices and formatted with the HFS+ file system. Under MS-Windows and some unix systems, SD cards can be formatted using the NTFS and on later versions exFAT file system. However most consumer products will expect FAT16/FAT32 filesystem.

Can I format my SD card?

Yes. Generally, Windows XP, Vista and Windows 7 can be used to format your SD card, and you can often format the card in your device of choice: for instance, your camera may have a formatting utility. The default settings should be used.

If you experience problems reading your card after formatting, we suggest trying the SD Card Association's SD Formatter software.
 You can download it free here:

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Should I defragment my SD card for better performance?

No.  It is unnecessary to use any disk optimization tool because, on an SD card, the time required to access any block is the same. Defragmenting an SD card will wear out the card slightly, as the number of writes are limited before failure occurs (about 100,000 times).

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Do all computers read SD cards? How can I tell what my computer will read?

Most computers made in the last two years have a built-in SD card reader. However, if you do not own an SD card reader, you can often use the SD card reader in your digital camera by plugging your camera into your computer with a USB cable, or purchase an SD card reader that attaches to your USB port from any electronic retailer. As of this writing, excellent SDHC card reader/writers are available online for about $20. Make sure that your device that supports SDHC as well as SD. Only the SDHC readers will read cards beyond 2GB.

Important:  not all devices advertised as "SD Card Readers" also write to an SD card, which is a disappointment if you hope to save data from your computer onto your SD cards.  Make sure that the SD card drive that you order is both a reader and a writer.  If the product description omits the write capability, the device is probably read-only.

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Will SD Cards work on Macintosh computers?

Yes.  These Apple computers include SD Card slots:  MacBook Pro (13-inch, Mid 2009), MacBook Pro (15-inch, Mid 2009), MacBook Pro (15-inch, 2.53GHz, Mid 2009), iMac (21.5-inch, Late 2009), iMac (27-inch, Late 2009).  For complete information about Macs and SD Cards, please see:

You can also attach an SD Card Reader to a Mac's USB port.

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Can I use an SD Card with my Apple iPhone?

Yes, but the iPhone requires an SD Card Reader available here:    

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Can I use an SD Card with my Apple iPad?iPad with SD Card Reader

Yes.  The iPad requires the iPad Camera Connection Kit ($29 from Apple), which includes an SD Card Reader
and a USB connector.  

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Can I send photos to a digital photo frame with an SD card?

Yes - as long as the photo frame has an SD card reader (and most do.) Services like are a terrific way to send photos to a digital photo frame since, out of habit, most people never actually update their photo frames with new photos. If you are sending an SD card to an unknown photo frame, we suggest that you stick with a 2GB card, and send moderately sized images. Even an 8x10 photo frame would not require images larger than 1200 by 1500 for an excellent display. A 2GB SD card will hold thousands of these photos.

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I can't read or write to my SD Card. What's wrong?

  1. SD cards look the same, but they come in two formats: "SD," which have a capacity up to 2GB and "SDHC" with higher capacity up to 64GB. Test your card in another device to see if it reads and, if your reader is more than two years old, consider upgrading your reader to an SDHC device. You may also need to upgrade your computer's BIOS to use the newer reader.  Some older readers may not read cards that are 4GB or larger.  Cards with a capacity of 4GB or larger must be used in SDHC devices. Non-SDHC devices are not programmed to handle 4GB or larger cards and therefore cannot correctly identify SDHC or SDXC cards. Also, make sure that your card is properly formatted (see formatting questions).
  2. You may have applied a password to the card or to the file. Remove the password.
  3. The card may be damaged. See this helpful page:
  4. If you cannot write to the card, you may own a "reader," but not a "writer."  Check your manual, or try to the write to the card on other device;  if you can write to the card on another device, you probably own a read-only device.  
  5. If you cannot write to the card, your write-protect tab may be set to "on." The write-protect tab is on the left side of the side of the SD adapter card.  Slide it in the other direction and re-insert the card. The adapter card may also be damaged; try another adapter card or remove the microSD card and try it in a device that accepts a microSD card such as a phone.
  6. You may have "Safely Removed" your hardware in Windows.  See this question for details.
To recover your data, try this tool:

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Which SD Card reader do you recommend?

We like the SIIG Internal Reader available for about $20.  It includes an internal USB cable that will plug directly into your motherboard and an adapter cable that can plug into an external USB port.  

The SIIG JU-MR0112-S1 All-in-one USB 2.0 Card Reader claims, "All-in-one drive bay design provides easy access to different types of memory cards, Plug and play on Windows and Mac systems, no drivers needed, Supports SDHC and CF v4.0 (HSCF with Ultra DMA mode)."

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Do TVs read SD cards? Can I save videos on SD cards?

Many digital televisions including most Panasonic sets now contain an SD card slot. You can save videos to SD cards, and, even if your TV can play them, you can play videos from SD cards through most game machines or by attaching a video camera.

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Do music players, ebooks or portable media players read SD cards?

Most new electronic devices play SD cards: eBooks, cell phones, music players, video cameras, game machines, exercise equipment, digital cameras and even binoculars. Many of these devices are now merging into a single device that will play or display most popular media. For instance, as of this writing, Creative's 8GB Zen MX Portable Video MP3 Player retails at for $59.95; its SD card slot accepts up to 32GB cards. The color Nook, the eBook from Barnes & Noble, and the latest Sony Readers contains microSD card readers.  (Check manufacturer's specifications prior to purchase.)  SD Card readers make it easier to expand your device and control your own content.

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How can I play high definition videos from SD cards on my television?

Envizen Hi-Def SD Card PlayerEnvizen's EMC 01 (about $100) plugs into your TV like a DVD player or VCR and plays movies from SD cards. SD cards hold more data, take up much less space and are more reliable because they do not rely on mechanical parts.

H816 SD Card Player
The H816 generic SD card player also attaches to your television and sells for about $45.

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How can I convert my videos to SD format?

The $100 iConvert Video Convert device turns older VHS and DVD formats into SD Cards.

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How long will SD Cards hold my information?

The SD Card Association notes: "SD cards, like most semiconductor cards, store information in flash memory. The current technology along with normal usage typically gives the card a lifespan of 10 years or more."

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Can I reuse SD Cards?

Yes. You can add information to available space on an SD card, or you can overwrite your information. SD cards can be re-written about 100,000 times.

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What can I print on my SD Card label?

Some suppliers enable you to customize your SD Card label.  For instance, at, each SD Card label can include up to four lines of 12 characters each.  You can choose the default label text that contains:
  1. Your first name
  2. Your last name
  3. Your city
  4. Order date and card size in gigabytes
You can also edit the default text or delete the text entirely to create a blank label.

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What if my microSD card gets separated from my labeled full-size adapter card?

Using Notepad or another text editor, add a small text file to your microSD card that identifies your microSD card.  This way, if the microSD card is separated from its labeled full-size SD Adapter, you'll be able to quickly identify the card, and put the correct microSD card back into the labeled SD Card adapter.

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How do I upload a video from my cell phone SD card to my computer? My media player will not play the video file.

Your media player is designed primarily to support the files that its manufacturer wants to sell.  Here is a free open-source media player that plays most files captured by cell phones:

There are also conversion tools for videos, but they can be expensive, time-consuming and tricky.  Try a better media player first.

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How do I put music on my SD card with only an SD card and a Wii with Internet access?

The Wii does not have a music service that saves music to an SD card.  However, if you have a computer, here is a way to get music onto a Wii SD card that you can play on your Wii:

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What's the difference between SD and SDHC?

The SDHC specification was completed in June 2006, but, by that time, non-standard high-capacity (>1GB) SD cards (based on the older 1.x specification) were already on the market. The two types of storage cards were not interchangeable, creating some confusion among customers. Fortunately, such cards were expensive and represented a very small portion of the SD-card market, giving vendors of consumer devices and storage cards time to adopt the SDHC SD2.0 standard.

SD and SDHC cards and devices have these compatibility issues :
  • Devices that do not specifically support SDHC do not recognize SDHC memory cards.Some devices can support SDHC through a firmware upgrade.
  • SDHC devices are backward compatible with SD memory cards.
  • Some manufacturers have produced 4 GB SD cards that conform to neither the SD2.0/SDHC spec nor existing SD devices.
  • File System: SD cards are typically formatted with the FAT16 file system, while SDHC cards are typically Hi, Joe, did you see this? formatted as FAT32. However, both types of cards can support other general-purpose file systems, such as UFS2, ext2 or the proprietary exFAT for example.
  • Microsoft Windows may need a hotfix to support accessing SDHC cards.
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I cannot see my SD card reader in Windows.  How can I fix that?

If you have an older "SD" card reader, it will still not be able to see SDHC cards that are 4GB or larger.  Look up the capability of your SD reader on the Internet or test to see if it will read a 2GB card;  if the 2GB card reads, but larger cards do not, you may need a new reader.

If you have clicked on the Windows icon that enables you to "Safely Remove Hardware" prior to removing your SD card from its slot, you may have actually "removed" the card reader itself.  This is a common confusion because it appears that the SD card itself cannot be read.  The solution is to uninstall the card reader, re-boot your computer, and let the computer "find" the card reader again.  Here's how:

  • Click on the Start button (must be administrator)
  • Right-click on My Computer
  • Click on Manage.
Manage Windows Computer
  • Click on Device Manager
  • Find the USB or Mass Storage Device with the Exclamation Point
  • Uninstall the Device
  • Re-boot the System
  • The system should re-install the card reader upon re-boot.
Uninstall SD Card Reader

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