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Whether for a phone, a camera, or some other gadget, shopping for microSD cards seems like a pretty simple thing to do, right?

Yet there’s a lot more to them than you might realise, and it’s surprisingly easy to wind up falling into a number of traps: overpaying, terrible performance, or the card not working at all.


Part of the reason is the number of specs related to memory cards 10 Things To Know About Digital Camera Memory Cards 10 Things To Know About Digital Camera Memory Cards Read More . So let’s take a look at how to read these specs, how to determine which one is right for you, and which mistakes to avoid.

1) Buying Incompatible Cards

When you talk about microSD cards, you are mostly talking about the form factor. All microSD cards fit into all microSD card slots, but they won’t all work. There are three different card formats, as well as different standards, that determine compatibility.

The three formats, which you’re probably already familiar with are SD, SDHC, and SDXC (or microSD, microSDHC, and microSDXC, but both micro and full-size cards are based on the same spec). Each format is defined in the SD specification, but they don’t work in the same ways.

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As a result, the formats are not backwards compatible, and you cannot use newer cards in hardware that only supports older formats.

sd formats

The differences between the three formats are significant:

  • microSD: Has a capacity up to 2 GB, and can be used in any microSD slot.
  • microSDHC: Has a capacity of more than 2 GB and up to 32 GB, and can be used in hardware that supports either SDHC and SDXC.
  • microSDXC: Has a capacity of more than 32GB and up to 2 TB (although at the time of writing this, 512 GB is the largest available card), and can only be used in devices that support SDXC.

In addition to checking that a card’s format is compatible with your hardware, you need to check a few other details, too.

Physical Size

First, hardware that supports microSDXC slots won’t automatically support every size of card in this format. The HTC One M9, for example, officially supports cards up to 128 GB and might not work with anything larger.

sandisk ultraplus

And if you’re planning to use your microSD card with your PC at any point — for example, to move files on and off — you also need to ensure your PC supports the file system From FAT To NTFS To ZFS: File Systems Demystified [MakeUseOf Explains] From FAT To NTFS To ZFS: File Systems Demystified [MakeUseOf Explains] Do you really know what your hard drive does whenever you read a file from it or write one to it? Our hard drives can now store massive amounts of data, and that massive space... Read More that the card is formatted with. MicroSDXC cards use the exFAT system by default. Windows has supported it for over a decade, but OS X only since version 10.6.5 (Snow Leopard).

Ultra High Speed

The SDHC and SDXC formats can support the Ultra High Speed (UHS) bus interface — faster circuitry that enables data to move at a quicker rate. The two versions of UHS are UHS-I (with bus speeds of up to 104 MBps) and UHS-II (up to 312 MBps).

In order to benefit from the increased performance of UHS, it needs to be supported by your hardware. UHS memory cards will work in older slots but with a reduced bus speed of 25 MBps.

2) Choosing the Wrong Speed

Identifying the speed of a microSD card is just as complicated as deciphering formats and compatibility. There are four ways to show how fast a card is, and it’s not uncommon for manufacturers to use all of them.

class icons

Speed Class

The Speed Class shows the minimum write speed of a memory card in megabytes per second. There are four Speed Classes defined as follows:

  • Class 2: At least 2 MBps.
  • Class 4: At least 4 MBps.
  • Class 6: At least 6 MBps.
  • Class 10: At least 10 MBps.

Showing base level performance helps you to identify whether a card is suitable for a specific task, but because it makes no comment on maximum speeds, it’s technically possible for a Class 2 card to be faster than a Class 6 card. Class 10 cards should be noticeably faster, though, as they have a bus speed of 25 MBps (compared to 12.5 MBps on Class 2 to Class 6 cards).

uhs speed

UHS Speed Class

UHS Speed Class shows the minimum write speed for microSD cards that support the UHS-I and UHS-II bus speeds. We’re listing it as a separate category because some manufacturers list both classes on their cards. The two UHS Speed classes are:

  • U1: At least 10 MBps.
  • U3: At least 30 MBps.

Rated Speed

While it’s generally safe to assume that a higher Speed Class correlates to faster all-around performance, and UHS cards faster still, some manufacturers also quote a maximum speed for their products.

These speeds are shown in megabytes per second and help you pick out the absolute fastest cards. The speeds are based on manufacturer tests, however, so they may represent a best case scenario rather than real world performance.

kingston speed

In practice, there are other external factors that will affect read and write speeds. If you’re copying files to your PC, for instance, your PC’s specs — and even the USB cable you’re using — will play a role.

Relative Speed

The other way manufacturers show the speed of their cards is a throwback to the old CD writing days No DVD Drive on Your Tablet or Notebook? Use an Old Laptop Drive Instead! No DVD Drive on Your Tablet or Notebook? Use an Old Laptop Drive Instead! More and more Windows computers are shipping without optical drives, and this is a phenomenon that exists beyond the tablet PC. The lack of a DVD drive might prevent you from installing your favourite apps... Read More .

The original transfer rate for CDs was 150 KBps. As drives developed, they would advertise themselves as being 2x, 4x, 16x, and so on, showing how many times faster than 150 KBps they were.

MicroSD cards are also often labelled in this way. When a card is described as 100x, it means 100 x 150 KBps, which is 15 MBps. That speed is, again, under ideal lab conditions.

3) Wrong Cards For the Task

When buying a microSD card, it’s important to pick one that is right for its intended use How To Choose The Right SD Card For The Job How To Choose The Right SD Card For The Job SD cards aren't all about storage! In fact, there are several other factors to consider, and when purchasing your cards, you should make yourself aware of them. That said, SD cards aren't all created equal,... Read More . This means finding a card that is large enough and fast enough — not necessarily the largest and fastest card out there. High capacity UHS-II U3 cards often still have a price premium and you won’t always notice the benefits they offer.

If you’re using a microSD card to increase the storage on your smartphone, then it makes sense to pick the highest capacity you can. At the same time, speed won’t be a major priority since you won’t be transferring large files back and forth frequently.

The exception would be if you’re using a newer phone that can shoot 4K video Live Photos & 4K: Why You Shouldn’t Buy a 16GB iPhone 6s Live Photos & 4K: Why You Shouldn’t Buy a 16GB iPhone 6s If you want to take advantage of the new iPhone 6s camera, you'll probably want to avoid picking the 16GB storage option. Read More . Just as with a 4K video camera (like the GoPro Buying a GoPro or Action Camera: 7 Useful Things You Need To Know Buying a GoPro or Action Camera: 7 Useful Things You Need To Know If you're into skiing, cycling or surfing, then an action camera is the perfect way to record your adventures. Read More ), large capacity and high speed are musts.


Panasonic recommends UHS Speed Class 3 (U3) for shooting 4K video. For full HD video, it suggests Class 10 or Class 6 at a push. If your card’s write speed is too slow, it will result in dropped frames and produce stuttering video.

For photography, some users prefer several smaller cards to a single large one so they minimize the risk of losing all of their photos if a card corrupts. If you’re shooting RAW, where files might be 20 MB or more Budding Photographer? Here's Why You Should Be Shooting Raw Budding Photographer? Here's Why You Should Be Shooting Raw Every dSLR, prosumer and even some high-end compact cameras have the ability to save raw image files. This isn't just a higher quality of image, it's a gift from the photography gods. Read More , you’ll benefit from having U1 or U3 speeds (but they require at least SDHC format).

lexar microsd

And in case you’re wondering, there’s no difference between a full-size SD card and a microSD card in an SD adapter. If your camera only has an SD slot, you can still use a microSD card in it.

4) Buying Fake Cards

It sounds like an obvious thing to avoid, but sadly, buying fake memory cards is incredibly easy.

If you find a good deal on branded memory cards from a non-reputable seller, then there is a real risk that it may be counterfeit. In fact, a few years ago a SanDisk engineer reportedly stated that as a many as a third of all SanDisk-branded cards were fakes. It’s unlikely that that number has declined since.

The buying guides on Ebay include a page on spotting counterfeits due to how common they are. Amazon Warehouse sellers have been accused, too. If you’re buying from a source you’re unsure about, check the reviews first.


Counterfeit cards are configured to report the capacity that is printed on the packaging, but actually contain far less. You won’t notice this until the card fills up unexpectedly quickly.

Use the utility H2testw for Windows, or F3 for Mac and Linux, to check that the cards you already own are genuine.

5) Cheaping Out on Brands

We’ve all owned flash memory cards that have stopped working for no apparent reason. While reliability is generally excellent, microSD cards do fail Hard Drives, SSDs, Flash Drives: How Long Will Your Storage Media Last? Hard Drives, SSDs, Flash Drives: How Long Will Your Storage Media Last? How long will hard drives, SSDs, flash drives continue to work, and how long will they store your data if you use them for archiving? Read More , and when they do, they’ll take all your data with them.

For this reason, buying cards from big brands is always better than buying no-name cards for cheaper. You can expect better performance, greater levels of reliability, as well as more robustness, with cards routinely protected against shock, water, and even airport X-rays.


You also get things like a lifetime warranty (where your card will be replaced if it fails) and access to image recovery software (to retrieve data from a damaged or corrupted card). Manufacturers such as Lexar and SanDisk offer this as standard.

What’s Your Perfect MicroSD Card?

There are many things to consider, but once you understand things like speed, specs, and all of the other issues, it becomes much easier to narrow down your options and make a choice.

As a general rule, it’s always a good idea to buy specific cards for specific tasks. This way you can guarantee the best combination of speed and capacity for your hardware to give you the best possible overall performance.

What do you look for when buying microSD cards? Have you ever encountered compatibility problems or fakes? Let us know in the comments.

Image Credits: Sandisk Ultraplus via, Lexar cards via

  1. Garry Cowan
    December 2, 2016 at 11:51 am

    Bought a 32gb card from Amazon and encountered lots of reliability problems kept failing and had to repeatedly uninstall it from phone I installed card recognition app to find it wasn't the brand proportedon the packaging. Had to replace it with a relatively pricier model from a reputable shop in retrospect I should have done this the first time.

  2. Dibbendu Koley
    November 1, 2016 at 6:33 pm

    Did you said that micro SD card and big SD cards will work the same (if compatible). If I use an adapter to use micro SD in camera it will work like big SD card???

  3. Alan
    October 13, 2016 at 7:22 am

    Add that you should never use a SanDisk Ultra microSD card in a dashcam and you could name the article 6 Mistakes to Avoid... I've had 3 go bad so far. They can't handle the abuse of the constant writing of HD video. I've t switched to Transcend High Endurance cards for my dashcams.

  4. Perry
    August 30, 2016 at 4:00 am

    So many fakes on the market. I bought a 16gb in coles that was packaged as 16GB and turned out to be 8GB when i got it home :-(

  5. Christof88
    August 1, 2016 at 8:17 am

    "In order to benefit from the increased performance of UHS, it needs to be supported by your hardware. UHS memory cards will work in older slots but with a reduced bus speed of 25 MBps."

    So, does the samsung galaxy s3 i9300 have such a reduced bus speed? In other words, is it worth it to invest in a "Extreme Pro SDXC 128GB, 95MB/sec class 10 UHS I" for instance, will I ever get to the claimed 95/90mbps speed and does my type of smartphone even need that?

    I will be using it quite a lot to transfer FLAC music files back and forth so it could really be a timesaver.

    Thank you to all who are kind enough to reply.

  6. aapreetam
    July 25, 2016 at 11:29 am

    it was used in android mobile and now not reading writing .

    Now i install it in java feature phone samsung GT-c3312 , In it although showing folders according mobiles as my moovies , videos etc but after copy any thing it gone out .

    a have a micro SDHC card of 4 GB , it always showing viruses as new folder etc in computer it showing 3.67GB free of 3.68 GB as we format it with format/q but show 3.67 GB and that new folder file as it . I tried with computer manage it shows it 3.69 GB , it format but in last after 99% showing bad (fat32, 4096 bytes) . I tried to format with dos command exfat / 32k ; it starts and in last show failure in 0 sector.

    I tried with norton AV but it don't show any error on it .

    pl help me how format it , with software or specifications.


    I tried with SDHC download software but it shows protected file and fails.

    pl help how format so it will usable

  7. Robaye
    July 24, 2016 at 1:10 pm

    I was shocked how picky Roku 3 is with memory. 3rd try was finally a success from MicroCenter. Emtec 8MB Class 4. No luck with Microcenter brand nor SanDisk.

  8. shakes
    July 4, 2016 at 3:34 pm

    are you having an epileptic seizure? Can you shake any more?

  9. MS
    June 27, 2016 at 7:24 am

    Can any SD cad reader read/write to any MicroSD cards. My card reader cannot copy or read files from 8GB or larger capacity SD cards. Has anyone experienced the same? While it detects the card and open it when trying to copy files from or paste into get sudden crash.

  10. anju
    June 21, 2016 at 11:16 am

    Please suggest good sd card for moto g 3rd gen

  11. Nanath Jayawickrama
    June 4, 2016 at 1:36 pm

    i'm going to buy a 2TB sdxc card to put to my htc one m8....just wanna know if it's compatible !!
    please help me!

    • Functional Member of Society
      June 5, 2016 at 10:06 pm

      Jesus, use google, will ya?

      • Nanath Jayawickrama
        June 9, 2016 at 1:49 pm

        wow, i thought this site was to get help !!! if i cud find it in google i wudnt be here would i now???

        • Elaine
          June 9, 2016 at 8:34 pm

          You totally sound like you are making everything up. People who can afford to buy stuff wont be asking stupid questions in forums. You are at best someone seeking attention. And obviously this post wont change that.

        • Darwin
          October 15, 2016 at 7:52 am

          Elaine, really? It would have been simpler to just give him a short quick answer. However, it is widely known that people that put others down are the ones seeking attention.

    • Darwin
      October 15, 2016 at 7:50 am

      The card may be compatible but probably will not read the full size of the card. You have probably already done this research but are justified to an answer that does not look down on you.

  12. Gadgety1
    June 1, 2016 at 8:51 am

    My 128GB SanDisk microSD SDXC failed. I get a refund of the value on the guarantee, but "access to image recovery software (to retrieve data from a damaged or corrupted card). Manufacturers such as Lexar and SanDisk offer this as standard." Sandisk Recovery Service is $375.

    • Dan
      July 11, 2016 at 2:31 am

      Make a habit of backing up your phone every week.

  13. Garima
    May 27, 2016 at 7:01 pm

    Hey there, I am using Lenovo A6000 and I want to buy a 32 GB memory card for my mobile phone.
    Can someone help me to decide which card should I buy?

    • Dibbendu Koley
      November 1, 2016 at 6:17 pm

      You can buy SanDisk ultra SDHC class 10, it's around 1k in Flipkart. It's reliable and working good. I have suggested the same card to two other friends they also found it good. I'm using this for 2 years now and it worked in my motoe2 as well as in my Lenovo K4 note. Hope it helps...

    • Dibbendu Koley
      November 1, 2016 at 6:20 pm

      Buy SanDisk ultra SDHC class 10. It works very well. I'm using it in my Lenovo Vibe k4 note.

  14. Charles
    May 20, 2016 at 9:28 am

    Thanks for this informative article. However, I would like to know if a MicroSD card reader can read MicroSDHC cards or not.

  15. John P Dolden
    May 18, 2016 at 10:23 am

    Hi, I own a Samsung Galaxy J5 which has a capacity of 128 GB. I seem to be unable to buy a 128 GB SDHC card for this, as they all seem to be selling only SDXC at this capacity. Or does anybody know differently? I notice many sellers list these as SDHC, but on the picture you can clearly see SDXC, regards, John

    • ANDY
      May 18, 2016 at 11:39 pm

      SDHC=4gb-32gb SDXC=32gb or larger. It's just a technically name to indicate the capacity of the card and speed is totally different story. I'm sure they listed wrong.

  16. xaris2000
    May 4, 2016 at 10:06 pm

    Really helpful thread.Thumbs up from Athens.

    • HughR
      June 4, 2016 at 8:23 am

      Agree, very helpful overview. I was copying over music to a 128gb card, and it crapped out near 8gb. I thought it was my old machine until this article. Cheers.

  17. krisko
    April 13, 2016 at 10:49 pm

    I don't understand why do we need UHS cards for shooting 4k video? A typical 4k bit rate would be 30 mbps or not more than 4MBs fo which a class 4 SD card would be perfectly OK.
    Why do we need speeds of 30 or 48 or even 90 MBs ? Is this uncompressed bit rate ???

    • Naud
      May 2, 2016 at 3:51 pm

      4K uses about 6MB/s on my Samsung Galaxy S7. Professional video cameras would likely use much more than that. MicroSD cards with speeds of 80-90 MB/s aren't that expensive anyway.

  18. Paul Fowler
    March 17, 2016 at 11:52 pm

    Thanks for this very informative article. For some time I have been stymied by a number of micro SD cards I received as surplus from my daughters company. I was trying to format 32GB micro SDHC cards with a Micro SC adapter and all of them failed. Now I understand why and just purchased an SDHC adapter to see if it will solve this problem.

  19. john
    March 14, 2016 at 7:26 pm

    Does anybody know which one is the perfect for the new galaxy s7 in order to shoot 4k videos?

    • Andy Betts
      March 14, 2016 at 8:37 pm

      I believe the bitrate of 4k video on the S7 isn't too high. It's 48Mbps, which is only 6MB per second. I'd probably go for something like a sandisk Extreme, which should do the job nicely, though you could get something slower if you're on a tight budget.

      • Sean
        July 29, 2016 at 8:17 pm

        The patriot lx series brand card sold on amazon and fulfilled only by amazon. Is what I only use in my S7.

  20. Mosi
    March 3, 2016 at 3:28 pm

    Does anyone have recommendations for what has worked well for a Raspberry Pi?

  21. Vicente Olmos
    December 21, 2015 at 11:31 pm

    And if I use a SDXC card (exFat) in a camera and connect the camera via USB to a PC (Windows 7) having a NTFS drive, may I expect that the file transfers will work?

    Vicente Olmos, Madrid, Spain

  22. cowbutt6
    October 26, 2015 at 1:22 pm

    I've used SDXC cards with devices that only claimed support for upto 32GB SDHC twice now - a Samsung Galaxy S II and a 3rd gen Moto G. Naturally, the card had to be reformatted as FAT32 rather than the default exFAT, as neither supported the latter filesystem, but otherwise usage was trouble-free.

    • John
      January 13, 2016 at 3:18 pm

      Yes, exFat will be readable and writeable both in linux (android) and windows.

  23. Howard Blair
    October 25, 2015 at 6:11 am

    "Counterfeit cards are configured to report the capacity that is printed on the packaging, but actually contain far less. You won’t notice this until the card fills up unexpectedly quickly."

    Worse yet, the filesystem will "loopback," overwriting the files on the disk while still reporting the first files written (which have been lost).

    One eBayer bought a "pocket hard drive" which had a tiny USB drive inside, and two metal nuts to hold it in place.

  24. Zakir Hosen
    October 24, 2015 at 12:41 pm

    HI Andy,
    Great article and very informative. Its true that sometimes we don't bother for the memory cards but its very important to buy a good branded and good quality of higher class of memory card to secure your memory and to faster data transfer. I must say very well written and personally i used 64GB [ ] which is really good so far and i am fully happy with that but in some cases few cheap Chinese memory card can't perform as it written. I had a very bad lesson with that kinds of cheap card and after that i am using the above memory card which i am using on my S4 and its almost a year now and i didn't face any issue.
    Finally i must say everybody should know the above facts before buying a memory card. Thank you Andy once again for your details information and examples.

    Zakir Hosen

  25. Kevin Verwey
    October 24, 2015 at 10:28 am

    Very useful, however one thing that bothers me, is the 'HTC One M9' up to 128gb, which is not true; it supports to 2tb since launch, i'm using a 256gb card and it is working normally.

    • Ben Leverett
      October 24, 2015 at 4:45 pm

      Well, in the last section of the paragraph labeled size, what you said is kind of a moot point, because there is a vast amount free premium partitioning softwares out there, nowadays.

    • Nathan_G
      October 13, 2016 at 12:53 pm

      Indeed, that is a significant error in this article. The HTC One M9 does support up to 2 TB and has since launch. The author needs to fact check better. Though it's not too important in the scope/setting of this article except to the owners of a HTC One M9. Like us :)

      • Wumpus
        December 3, 2016 at 11:46 pm

        I have had an HTC One m9 since release, but no one, AFAIK can buy a 2TB card yet for it, because there are none available, and won't be for at least another year. It is *expected* to support it, but no one can say for sure that it will. Maybe 512GB will work (whenever it eventually comes out), but even that's not guaranteed. So, fact-checkers, just because the marketing people say something doesn't make it true. For example, many people voted for Pedro, but all their wildest dreams didn't come true. Fact checking has sadly been reduced to proficient googling without any corresponding skills in using common sense.

  26. Rakesh Malhotra
    October 24, 2015 at 6:12 am

    Very useful and well written.

  27. On Ting Wong
    October 23, 2015 at 4:32 pm

    Very informative. Thank you very much!

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