Fastest microSD Cards | Top 7 as of April 2021
These are the current fastest microSD cards I’ve come across so far in my independent speed tests:
- Delkin Devices Power V90
- Lexar Professional 1800x U3
- Verbatim Pro+ II V90
- ADATA Premier ONE V90
- Kingston Canvas React Plus V90
- Silicon Power Superior Pro V90
- ProGrade Digital V60
These are ranked by tested sequential write speed results. That’s the measure that’s most relevant to recording 4K, 8K, and high-bitrate video as well as fast photo burst modes. You can find more details below about each of these cards, as well as more information about how these tests were conducted.
What Are These microSD Card Speed Tests?
I try to buy and test as many SD cards as I can. This post is based on the results of those tests, and I update it regularly as I have the opportunity to test new cards. My focus here is on microSD cards that are well-suited to use in cameras for recording high-resolution video (4K and above) or burst sequences of photos. So I’m most concerned with sequential write speed rather than the types of write speed that some other applications need, such as gaming and computing devices.
There are quite a few devices these days that need fast microSD cards. From action cameras like GoPros to phones to gaming devices, a card that’s fast enough can help you make the most of your device. But there are several different types of speed when it comes to memory cards, and manufacturers don’t make it easy to compare apples to apples.
MicroSD cards are the smallest of the SD-style of memory cards. They’re about the size of a thumbnail and are commonly used in smartphones, gaming devices, and the smallest cameras like action cams. You’ll often see them referred to as microSDXC or microSDHC cards. That distinction doesn’t have anything to do with the physical size of the card–I have more on that below.
While the speeds and storage capacities of microSD cards have tended to lag behind the larger SD-sized cards, as they’ve become essential to more and more small devices, the card manufacturers have been improving microSD cards rapidly. They’re getting faster and coming in larger storage capacities. The SD Association has even created a new specification for future cards going up to a whopping 128TB of storage capacity. And with those increases in storage capacity have come significant improvements in speed. That means that they can better keep up with the high-bitrate video recording of 4K and 5K action cams (and, potentially, 8K ones as well).
Fastest microSD Cards | In Detail
Here are the ones that fill the top spots in my tests of sequential write speed, the measure that’s important for shooting high-resolution video. These are all more than fast enough for 4K and 5K video.
1. Delkin Devices Power V90 microSD Card
- Tested & Compatible in Android Smartphones, Tablets, the Nintendo Switch, Drones, DSLRs, Mirrorless...
- Uninterrupted 8K, 4K, 3D, HDR, 360º & High-Speed Recording
Delkin Devices isn’t as well known as some of the other brands that appear on this page, but they’ve been making flash memory cards for a long time. I’ve used several of their cards over the years and have always found them to be excellent. Headquartered in San Diego, they’ve typically focused on the higher end of the market. They’ve recently overhauled their memory card lineups into distinct categories; the Power line is for their fastest cards.
2. Lexar Professional 1800x U3 microSD Card
- Transfer content up to 9x faster over traditional action camera, USB cables with included USB 3.0 reader
- Great for 4K recording in aerial and action cameras
This card is very fast. But there are two catches. The first is that not all the sizes have the same speeds. I had originally tested the 128GB version and been somewhat surprised that its performance wasn’t better. A reader alerted me to the difference in speeds between the different sizes, so I tested the 64GB version. And that’s the one here. So if you want the fastest one, go with the 64GB size.
The second catch is that they’re not always easy to find, although that has been improving more recently. Lexar has been going through some corporate upheaval lately, including a change in ownership. I don’t know to what extent that has affected manufacturing and supply lines, but the upshot as a customer is that these high-end Lexar cards aren’t always as readily available as some of the other options here.
It comes with a UHS-II microSD-to-SD adapter cartridge (it used to come with a very fast USB thumb reader too, but that no longer seems to be bundled with it).
3. Verbatim Pro+ II V90 microSD Card
- V90 video speed class - supports 8K video recording
- UHS-II interface, U3 speed rated
Verbatim has a very long and impressive history in all manner of data storage media. But they haven’t put the same amount of consumer marketing oomph behind their memory cards that they used to do with floppy disks and CD-Rs. But they know what they’re doing, and this is a very fast microSD card.
It’s rated to V90 and has a UHS-II interface. It comes with a microSD-to-SD adapter, but the adapter is only UHS-I, which seems like an odd choice. I haven’t found this card widely available at many retailers. If you do find it, make sure it is the Pro+ II version (it will be printed on the card, and it’s UHS-I). There’s a big jump in performance from the regular Pro+ V30 UHS-I version.
4. ADATA Premier ONE V90 microSD Card
- Supports SD 4.0 UHS-II standard and latest V90 Video Speed Class.
- Max Read up to 275MB/s, 3 times faster than UHS-I cards. *Max speeds only when paired with UHS-II...
The ADATA brand is relatively new to memory cards–at least ones that are readily available–but this Taiwanese company has been in the flash storage business since 2001. They don’t have a particularly large retail presence, but they seem to be focusing on the fast end of the market. This particular card is very fast. I haven’t used ADATA cards enough in real-world shooting to form my own opinion as to their reliability, but I’ve heard good things from others.
5. Kingston Canvas React Plus V90 microSD Card
- Ultimate speeds to support professional camera use — Transfer speeds up to 285MB/s and recording speeds...
- UHS-II standard for reliable high-resolution photography and video recording — Capture 4K and 8K...
I’ve used Kingston memory cards on and off for many years. And while I’ve always found them to be reliable and cost effective, they haven’t tended to aim toward the fastest end of the market. That’s changed with these Canvas React Plus cards, which are aimed at 4K and 8K video shooters.
It’s a UHS-II card and comes with a USB reader as well as a microSD-to-SD adapter cartridge (the cartridge is, oddly, only UHS-I).
7. Silicon Power Superior Pro V90 microSD Card
- The Future Is Here: 8K Ultra HD
- Read and write speeds up to 290 and 160 MB/s respectively. *Speed may vary due to host and device...
Silicon Power is a Taiwanese company that specializes in digital storage, with an emphasis on flash memory for consumer and industrial uses. Their memory cards that I’ve tried in the past have tended to aim at the middle of the market. This is by far the fastest of their microSD cards I’ve tried.
It’s a UHS-II card that carries a V90 rating and comes in 64GB and 128GB sizes.
Buy at: Amazon
8. ProGrade Digital V60 microSD Card
ProGrade Digital is a newcomer to the memory card space, but it’s not just another no-name brand that’s popped up from nowhere. It has been created by a team with incredibly deep experience in the industry–some of the key people who had been part of Lexar’s success but launched out on their own when Lexar was bought by a Chinese company. They’re focusing on the high end of the market with an emphasis on cards geared towards the top-shelf cameras and professional use. I’ve been very impressed with their SD cards as well, which are among the fastest SD cards I’ve tested so far.
Like the SD cards, I’ve found this UHS-II microSD to exceed their claimed speeds quite–and quite handily, at that. It comes in 32GB, 64GB, and 128GB sizes.
9. FreeTail Evoke Pro V60 microSD
FreeTail Tech is another company that’s specializing in fast cards to cater to the needs of high-bitrate video recording. Beyond that, I can’t say I know much about them—this is the only card of theirs I’ve tried so far—although their microSD cards seem to be harder to find. The first I’d heard of the FreeTail brand came from Panasonic GH5 shooters raving about their SD cards. The GH5 can shoot very high-quality video at very high bitrates–up to 400 Mb/s–which makes it very demanding of the memory cards you put in it.
This microSD card has performed well in my speed tests and is available in 64GB, 128GB, and 256GB sizes.
UPDATE: These cards have been hard to find lately.
10. SanDisk Extreme V30 microSD
- Up to 160MB/s read speeds to save time transferring high res images and 4K UHD videos (2); Requires...
- Up to 90MB/s write speeds for fast shooting; Requires compatible devices capable of reaching such speeds
SanDisk releases new models often, but they don’t refresh all of their lines simultaneously. That sometimes results in newer cards in lower lines leapfrogging older models in higher lines. That’s what’s happened here. The Extreme line is not SanDisk’s top line–that’s the Extreme Pro–but this new model has slightly improved speeds.
This card is rated for V30 video recording performance with rated speeds of up to 90 Mb/s sequential write speed and 160 Mb/s read speed.
11. SanDisk Extreme PRO V30 microSD
- Waterproof, shock and vibration proof, protected from airport x-rays, temperature proof
This latest version of the top-of-the-line Extreme Pro line is labeled both with V30 for 4K video recording and A2 rating for app speed. It’s rated for 90 MB/s sequential write speed and 170 MB/s sequential read.
SanDisk comes out with new models quite frequently, and there’s not always a lot of performance improvement between them (which is why there are so many near the top of the table below). This latest version claims a boosted read speed over the previous model, but the reality is that the past few iterations of the Extreme Pro have had much the same write speed, so if you can’t find this latest version, you can be confident getting a recent previous version.
12. SanDisk Extreme PLUS U3 microSD
- Storage Capacity: 64 GB
- Maximum Read Speed: 170 MB/s
The Extreme PLUS line of SD cards sits between the Extreme and Extreme Pro in SanDisk’s lineup (or used to–they seem to have done away with this series in the current lineup). As with the Extreme Pro, the performance of recent versions has been similar, so you don’t necessarily need this latest version (which is model SDSQXBZ).
SanDisk uses a three-part model numbering system in the format SDSQXBZ-064G-ANCMA. In this example, SDSQXBZ is the model, 064G refers to the amount of memory, and the last five characters are used by the marketing department for different parts of the world, but the cards are otherwise the same. So the first part is the crucial part if you’re looking to see which model the card is.
13. Samsung EVO U3 MicroSD
- Great-performance to capture, store and transfer videos, photos and music, for use in Smartphones,...
- Full-Size adapter included
Samsung isn’t known for action cameras (although they do have some interesting compacts and even 360° cameras), but they’re one of the very big players in the smartphone and mobile devices market, many of which use microSD cards. They’ve also got a lot of experience in flash memory and electronics in general. So it stands to reason that they’d make top-notch microSD cards–and they do. They have multiple models, and the distinctions between them isn’t always clear. This one is the EVO, and its model number is MB-MP, but you can also find models like the EVO Select and EVO Plus, which also work well.
Real-World microSD Card Speed Test Results
Below is the full list of my microSD speed test results. These are sorted by default by descending sequential write speed–the value that’s most relevant to using the cards in high-resolution cameras–but you can click on the column headers to sort by other criteria or use the search bar to filter by brand or model number. You can also scroll the table right to get the other columns.
|Brand||Model No.||Speed Class||UHS||Tested Write / Seq||Tested Read / Seq||Tested Read / But||Tested Write / Ran||Rated Read MB/s||Rated Write MB/s|
|ADATA||Premier ONE (AUSDX128GUII3CL10-CA1)||V90||UHS-II||219.8||278.6||261.0||9.0||275||155|
|Kingston||Canvas React Plus (MLPMR2)||V90||UHS-II||200.5||268.4||244.2||186.3||285|
|Silicon Power||Superior Pro||V90||UHS-II||140.0||251.0||198.7||4.1||290||160|
|SanDisk||Extreme PRO (SDSQXPJ)||U3||UHS-II||117.0||269.8||249.4||7.4||275||100|
|FreeTail||Evoke Pro (FTSD)||V60||UHS-II||116.1||272.1||250.5||5.8||240|
|SanDisk||Extreme Pro (SDSQXCZ)||V30||UHS-I||88.8||93.6||92.4||80.4||170||90|
|SanDisk||Extreme Pro (SDSQXCY)||V30||UHS-I||88.3||94.3||93.4||82.6||170||90|
|SanDisk||Extreme Pro (SDSQXCG)||V30||UHS-I||88.3||93.9||90.6||72.7||100||90|
|SanDisk||Extreme Plus (SDSQXBZ )||V30||UHS-I||88.3||93.8||93.7||83.1||170||90|
|Samsung||Pro Select (MB-MF)||U3||UHS-I||88.1||98.3||86.6||84.6||100||90|
|SanDisk||Extreme Plus (SDSQXSG)||U3||UHS-I||87.8||86.0||83||80.8||95||90|
|SanDisk||Extreme Pro (SDSDQXP)||U3||UHS-I||87.6||85.2||82.4||80.3||95||90|
|SanDisk||Extreme PLUS (SDSQXBG)||U3||UHS-I||87.4||91.5||90.8||86.4||100||90|
|Samsung||EVO Select (MB-ME)||U3||UHS-I||87.2||98.7||93.2||77.9||100||90|
|SanDisk||Extreme PLUS (SDSQXWG)||V30||UHS-I||87.2||91.0||90.3||85.3||95||90|
|Transcend||Ultimate 633x (TS32GUSDU3)||U3||UHS-I||73.7||91.1||87.7||18.2||95||85|
|Patriot||LX / PSF64GMCSDXC10||U1||UHS-I||71.0||92.8||91.4||64.9||85|
|Samsung||EVO Plus (MB-MC||U3||UHS-I||70.8||91.7||90.6||64.7||100||60|
|PNY||PRO Elite (P-SDU32GU395PRO-GE)||U3||UHS-I||55.3||88.1||81.6||3.7||95||90|
|SanDisk||Ultra Plus (SDSQUSC)||C10||UHS-I||50.3||92.2||88.7||12.9||80||-|
|Samsung||Pro Endurance (MB-MJ)||U1||UHS-I||35.2||95.1||94.2||36.4||100||30|
Obviously, this doesn’t include every microSD card available. It’s a growing list that I try to update regularly as new cards are released and become readily available. I buy all of these cards myself–there are no sponsored tests or freebies. If you have one you think should be added to the list, let me know in the comments, and I’ll do my best to track it down and test it.
Why Do You Need a Fast microSD Card, Anyway?
There are many devices where the speed of the microSD card doesn’t really make much difference. But there are some, like action cams or video cameras, where speed matters. If you’re using a microSD card in something like a GoPro or other camera or camcorder that records high-resolution 4K or even 8K video, some of the camera’s features might not even be available if you’re using a card that’s too slow. Or you might end up with unexpected stopping in video recording or other errors.
Just like with their bigger siblings, SD and Compact Flash cards, the speed of microSD cards varies widely from card to card.
The SD Association has tried to provide some standards that relate to speed, but even within those, there can be wide variation. The even-numbered class designations for SD and microSD cards, like Class 6 or Class 10, were supposed to provide an easy way to see if a card was fast enough for a particular use. And they did . . . for a while. But the capabilities of the newest cameras need something better than just Class 10. Most basic Class 10 cards won’t work well in 4K video cameras like the GoPro HERO9 Black, DJI Osmo Action, or Sony RX0 II, for instance.
So you really need to look further at the read and write speeds. Of these, the write speed is by far the most important for most camera uses. That tells you how fast you can get data on to the card. That doesn’t tend to matter as much when using microSD cards in smartphones or GPS units–or at least, that’s a different kind of write speed–but it does matter for cameras when you’re shooting in burst mode or recording high definition 4K video or super-fast framerates–or, most importantly, at high video bitrates. The read speed, which is often used in marketing and sometimes called transfer speed, tells you how fast you can get data off the card. That’s relevant when you go to download the footage or images, but it doesn’t tell you how the card can handle high-bitrate video recording or fast burst-mode photo sequences. With the speed tests and rankings below, I’m focusing on the sequential write speeds and basing them on my own independent real-world testing.
But manufacturers don’t always make it easy to see what the read and write speeds are. Names like “Ultimate,” “Power,” “Extreme,” “and “Pro, and “Elite Performance” aren’t particularly helpful, especially when speeds are improving so rapidly and manufacturers are recycling the same card names with newer cards with different specs. And some manufacturers advertise speeds measured in megabytes per second, while others use more cryptic multipliers like 1900x, making it hard to compare apples to apples.
So I’ve been putting some of the microSD cards that are most readily available to the test. Again, my focus here is on their speed for recording video and burst mode photos—there’s a different type of write speed that matters more for computing devices like smartphones.
Why Get a Fast microSD Card?
The newest cameras that are coming out have capabilities that can demand a lot from the memory card. Cameras like the new GoPro HERO7 Black or Sony RX0 can record at very high bitrates, and there are other cameras and devices that use even higher bitrates. These all require a fast memory card to keep up with the amount of data the camera is sending to it. If the card’s not fast enough, you can end up with issues like the recording stopping, the camera freezing up, or the camera overheating.
Because there are various ways of interacting with a microSD card, there are different types of speed. For transferring data off a memory card when you’re downloading to your computer, the sequential read speed matters. If you’re using it with a device running apps, you’ll be mostly concerned with its random write and read speeds. For recording video from a camera, the one that matters is the sequential write speed. That tells you how fast you can get data on to the card. It’s often not as clear as it could be, because the marketing departments for these manufacturers often use the sequential read speed in large, bold type on the packaging because that number is often higher and looks more impressive. But the read speed tells you how fast you can get data off the card, and that’s much less relevant when choosing a memory card that can keep up with the camera’s recording capabilities. So in ranking the cards here, I’m focusing on the sequential write speeds and basing them on my own tests.
But it’s not always true that the fastest card is necessarily the best card for what you need. Price and availability matter too. And then there’s the important issue of whether your camera can take full advantage of the card’s speed. There’s generally no harm in putting a very fast card in a slower camera because the specifications are designed to fall back gracefully and maintain compatibility. But the performance you get will be limited by the slowest point in the chain. To take advantage of what UHS-II cards can do, for instance, you’ll need a camera or reader that’s compatible with UHS-II. If it’s not, the card will still work–they’re designed to be backward compatible in nearly all cases–but you won’t get the highest speeds the card is capable of. One place you might see some benefit, though, is when you go to download the photos from the card to your computer using a card reader–but again, only if your card reader has a UHS-II interface.
About These Real-World microSD Speed Tests
In real-world use, a range of technical factors in the camera and its transfer hardware and software can prevent you from hitting the speed numbers on the card’s packaging. What I’m focusing on here is real-world uses, not scientific lab results that can’t be replicated in practical use.
In conducting these tests, my objective is to test the performance that we can realistically expect using off-the-shelf hardware in normal use.
There are two things I am not trying to do. I’m not trying to replicate the manufacturers’ benchmark lab tests. And I’m not trying to play gotcha and test whether the speed ratings the manufacturers claim are accurate. There are, after all, several things that can affect the speeds you can get out of cards in practice.
What I am trying to do is find out which cards perform best in real-world conditions and how they compare relative to each other. Because those are the things that matter to me when I’m trying to decide which card to buy. In short, I’m looking for practical speeds, not theoretical speeds.
So I’m using a real-world computer setup, not some high-end custom rig optimized to squeeze every last bit of bus transfer speed but not much good for actually processing photos and videos. There are dedicated hardware devices that exist only to test the speed of memory cards. Those are ridiculously expensive and not useful for any other purpose. Instead, I’m using readily available standard hardware that photographers might have on hand.
For the reader, I’m using a ProGrade Digital USB3.2 Gen. 2.0 Dual-Slot microSD UHS-II reader. It’s connected with a ProGrade Digital USB 3.2 Gen 2 Super Speed+ certified cabled via the Mac’s USB-C port. After extensive testing, I’ve found that this reader gives me the most reliable and consistent results, especially with the newer, faster cards.1
For the software, I’m using the benchmarking tools in Digital Media Doctor by LC-Technology, the company behind SanDisk RescuePro. All cards are new and freshly formatted with the SD Association’s official SD Card Formatter app. Because it’s quite normal for results to vary a bit between tests, I’m running each set of tests five times and averaging the results. And I’m using a 5GB data stream for each test.
For the computer, I’m using an iMac Retina 5K 2019 with an internal SSD. There are faster, more powerful computers that might squeeze out higher transfer rates, but this provides a useful real-world platform that is widely used and available.2
And, finally, the cards themselves. I buy all of these myself through standard retail. I don’t accept freebie cards or conduct sponsored tests.
Something not addressed in these tests is reliability. While flash memory is generally quite stable and resilient, in part, because there are no moving parts, memory cards can and do fail. When choosing which cards to use myself, speed is one factor, but I also generally favor cards from well-established brands. And for normal use, those typically offer excellent performance. But I also like to keep at least one spare on hand–it’s hard to complete a shoot with a faulty memory card.
But if you’re choosing a memory card for what amounts to near-constant writing–such as with a dashcam or security cam that is constantly being overwritten–you might be better off in the long run with one of the specialized high-endurance cards that some brands offer, like these. They typically aren’t at the top of the speed charts, but they add extra peace of mind that the card should be able to tolerate very high numbers of write cycles.
The Notes / Definitions
There’s a lot of jargon when it comes to memory cards. Here are some brief explanations that I hope provide some clarity.
All speed ratings I’m using here are in MB/s (megabytes per second), which is not to be confused with Mb/s (megabits per second). Megabits per second is the measure more commonly used by cameras and in recording video. There are 8 bits in a byte, so to get from megabits per second to megabytes per second, you multiply by 8. So 80MB/s is the same as 640Mb/s. Here’s a handy conversion calculator.
X Rating vs MB/s. Some manufacturers use a more cryptic x rating in place of MB/s. Lexar, in particular, has long used this system. It comes from the old way of measuring the speed of CD-ROM drives when the standard speed of a CD-ROM drive was 150KB/s. Each x, therefore, equals 150KB/s.
Here’s a quick cheat sheet for converting some of the common x ratings to MB/s:
SDHC vs SDXC
The codes microSDHC and microSDXC are useful as a practical way to determine what size card will work in your device. If your device specs say that it only works with microSDHC, then you’ll want a card that’s 32GB or smaller. If it says microSDXC, it’ll work with both.
But the designations are technically referring to the filesystem used on the cards as specified by SD Association guidelines.
SDHC (Secure Digital High Capacity) is a design specification that refers to SD cards that are between 4GB and 32GB in capacity and formatted with the FAT32 filesystem. FAT32 supports individual files up to a maximum of 4GB.
SDXC (Secure Digital eXtended Capacity) refers to SD cards with a capacity larger than 32GB and with a maximum theoretical limit of 2TB. They’re formatted in the exFAT filesystem.
SDUC The SD Association has also created a newer specification known as SDUC, for SD Ultra Capacity. It has its own host technology, protocols, and drivers, but in terms of card storage capacity, it’s designed to cover cards ranging from 2TB up to 128TB. SDUC cards will only work with devices that have SDUC compatibility specifically included, but you won’t find any of those cards in the wild just yet, so, for now, at least, you don’t really need to be concerned about accidentally getting one of those.
Technically, it’s possible to use a computer to format, say, a 32GB microSD card with exFAT or a 128GB card with FAT32. But doing so goes against the SD Association specifications, can cause problems in some cameras, and they’ll be overwritten to the appropriate standard next time you format the card in the camera. In general, I don’t recommend it. That said, if you really want to do it, I’ve put together a guide to using the official SD card formatter.
UFS vs microSD
UFS (for Universal Flash Storage) cards look very similar to regular microSD cards, but the internal memory is a different technology that can read and write simultaneously. Regular microSD and SD cards use a technology called eMMC that can only read or write at one time, not both together.
UFS isn’t widely used yet, and it’s most useful in devices that can take advantage of simultaneous reading and writing, such as smartphones and gaming devices, and even there, it’s still mostly used for internal memory rather than memory cards. With cameras, they’re usually writing or reading, not both at once. That said, the faster transfer rates in each direction would obviously be useful in cameras.
The important catch is that you can’t use a UFS card in a regular device unless the device is specifically compatible with UFS. And, for now, that’s only a handful of smartphones and specialized devices, not cameras.
Just like SD card, microSD cards are given a speed class rating that refers to its category for writing data, with each category describing a real-world video recording use. These apply the same to microSDHC and microSDXC cards.
Where things get a little complicated, though, is that these speed ratings don’t necessarily reflect the absolute speed of the card. Put another way, a card that has a V30 rating isn’t necessarily faster than one that has a U3 rating. That’s because to display the rating on the card, the manufacturers have to have their cards certified for that rating. It also involves revising packaging and marketing materials, which is an expensive process. So not every manufacturer will go to that trouble and expense right away. The upshot is that it’s not as simple as just looking at a card with a V30 or even V60 rating and knowing that it’s faster than one that only carries a U3 rating. It might be, but the rating system doesn’t work quite that way. You can see evidence of that in the speed test results on this page, with some cards with a lower speed rating being faster in testing than ones that display a higher speed rating on the packaging.
V90. The V-class is a new designation created to designate cards that are designed to work with the speeds required for high-bitrate 4K, 6K, and 8K video. The SD Association added some lower numbers to make them backward compatible with the older class designations (e.g., Class 10 and Class 6), but the most important ones are V30 and above.
Memory cards in the V90 class are rated to support a minimum sequential write speed of 90MB/sec. Their primary market is for cameras that shoot 8K video. For now, cameras that can shoot 8K are pretty rare, but the rating class provides room to grow.
V60 is applied to cards that support a minimum sequential write speed of 60MB/sec. They’re aimed primarily at cameras that record 4K video.
V30 is applied to cards that support a minimum sequential write speed of 30MB/sec. These are designed to support at least full HD video and some 4K video cameras that record 4K at lower bitrates.
U3 is designed to support 4K video recording at a sustained video capture rate of 30MB/s. This class overlaps with the newer V30 class.
U1 is designed to support real-time broadcasts and HD video (720p and 1080p) with a minimum serial write speed of 10 MB/sec. This overlaps with the newer V10 class.
Class 10 is designed to support 1080p recording at a minimum (but again, not at all framerates) with a minimum serial write speed of 10 MB/sec.
Classes 2, 4, and 6. Class 2 supports standard definition video recording with a minimum serial write speed of 2 MB/sec. Classes 4 and 6 are designed to support from 720p and 1080p video (but not all framerates) with a minimum serial write speed of 4 MB/s and 6 MB/s, respectively. Most newer cameras need cards faster than these, so memory cards in these speed classes aren’t as commonly available now.
The SD Association is regularly tweaking specifications to allow for faster and better performance from SD and microSD cards. In May 2020, they released an SD Express 8.0 specification with a dramatic increase in potential transfer speeds, allowing for transfer speeds of up to nearly 4000MB/second. It’s designed to be available on SHDC, SDXC, and SDUC cards. But for now, it’s just a spec and hasn’t yet been implemented in any consumer cards or devices.
What is the A Rating (e.g., A1 or A2)?
The A1 or A2 rating is a new type of speed specification that’s relevant for running apps from the memory card. The A rating is a separate specification, not one in the same sequence. So it’s possible for a card to have both A1 and V30 ratings, for example.
Up to this point, the primary market for memory cards has been for storing media like videos or photos. But increasingly, devices are able to run apps directly from a memory card. And that requires a different type of interaction with the space on the memory card–specifically, random read and write speeds and small chunks of data are placed wherever on the card there’s space for them.
So the new A specification (for App Performance) incorporates the random read/write speed. If you’re buying a memory card for a camera, it’s not especially relevant because what’s requires on those is sequential speed. So if you’re recording video (or shooting photos), the speed classes you want to look for are the ones starting with V (e.g., V30 or V60) or U (U1 or U3). But if you’re buying a memory card for a gaming device or smartphone or some other kind of device that runs apps and uses SD or microSD memory cards, the A1 or A2 rating is designed as a guide for what cards are best suited to that kind of use.
UHS-I vs. UHS-II
Newer microSDHC and microSDXC cards have a feature called ultra-high-speed bus, which refers to the interface. So far, there is UHS-I and UHS-II.
UHS-II is the newer, and potentially faster, system but adoption is still not widespread. And a UHS-II isn’t necessarily guaranteed to be faster than every UHS-I card in practice, as you can see from the test results above. The UHS-I category refers to a type of interface that has a potential maximum speed of 104MB/sec.
The product labeling for cards with this technology will have either UHS-I or UHS-II, or sometimes just I or II. Technically, it should be Roman numerals, but you’ll sometimes see it listed with a number 1, like UHS-1, even by some manufacturers.
You can also tell them apart by looking at the cards themselves. UHS-I cards have a single row of pins on the back.
But it’s important to note that taking advantage of the potential speed increases of UHS-II requires that both the card and the host (e.g., card reader or camera) support it. For now, at least, there are very few action cams (if any) that have UHS-II interfaces, so you won’t get the potential speed boost of the UHS-II bus. But the good news is that it’s backward compatible. You can use a UHS-II card in a camera that only supports UHS-II, but it will fall back automatically to UHS-I compatibility. Put another way: if you use a UHS-II card in a card reader or device that’s only rated for UHS-I, you’ll only get a maximum potential of UHS-I transfer speed.
Mini SD/miniSD vs Micro SD/microSD
You might come across mentions of mini SD cards. Most of the time, they’re actually referring to microSD–people sometimes use “mini SD” loosely to refer to the cards that are smaller than regular SD cards.
As a technical matter, there is such a thing as a miniSD card spec–it’s one of the three defined form factors that the SD Association has specced. But in practice, miniSD has been overtaken by the microSD form factor, and in nearly all cases–except the most highly specialized uses–what people mean when they’re looking for a mini SD card is actually a microSD card. You generally won’t find miniSD cards for sale in shops or online, and you’ll be hard-pressed to come across any devices that use them specifically.
MicroSDHC and microSDXC refer to cards of the same physical size. That distinction refers to the filesystem on board and is also related to the storage capacity of the card. There’s more information on that above.
General Recommendations When Buy and Using microSD Cards
- There are counterfeit memory cards out there. Buying from a reputable retailer helps minimize the risk of getting a fake.
- Memory cards are complicated electronic products. A small percentage of electronic products end up being faulty from the manufacturing process. So it’s good practice to test your card before using it in a mission-critical application. Better yet, have a spare (or spares) on hand as a backup. It’s a cheaper option than losing out on a shoot.
- Memory cards are not designed for long-term archival storage of photos and videos. It’s good practice to download the data as soon as practical and get it backed up securely.
- It’s always best practice to format memory cards in the camera you’re going to use them in, but if that’s not possible or not what you want to do, you can also format cards using a computer. But there are some things to know when formatting microSD cards to minimize the risks of your camera having problems with them. So I’ve put together guides on how to format microSD cards on Mac and how to use the free SD Card Formatter app for Windows or Mac.
- Previously, I was using a Lexar LRWM05U-7000 USB thumb reader. It’s one of the two options that come with the Lexar 1800x microSD cards. Although it’s UHS-II compatible, I found that I was getting inconsistent results from some of the newer, faster cards–especially UHS-II ones. After extensive testing of several different card reader and benchmarking software combinations, I found that I was getting much more consistent results out of the new ProGrade Digital reader. The top cards in this list, including all the UHS-II cards, have been retested using it. In addition, I’ve tweaked the testing routine to increase the datastream to 5GB for each test as well as increasing the number of tests from 3 to 5 (with the average taken). In a few cases, it has resulted in some revised results for write speeds (generally upwards and more consistent with the manufacturer’s claimed speeds). ↩
- Some of the earlier tests were done on an older computer, an iMac Retina 5K late-2014, with internal SSD. ↩
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