MicroSD cards are the smallest of the SD-style memory cards. They're about the size of a thumbnail and are commonly used in smartphones 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 has 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 with larger storage capacities--you can even get them up to 1 terabyte now. And they're getting fast enough to keep up with the high-bitrate video recording of 4K action cams.
For several years now, I've been making a point to buy and test as many different models of fast microSD cards as I can get hold of. This post is based on those tests. I'm focusing here on the sequential write speed, which is the one most relevant to recording 4K and 8K video in and high-speed bursts of photos, some of the most demanding uses of a microSD card's speed.
Fastest microSD Cards as of April 2019
These are the current top 5 fastest microSD cards so far according to my independent speed tests of sequential write speed. This is the metric that's most relevant to recording 4K, 8K, and high-bitrate video as well as fast photo burst modes.
Why Do You Need a Fast microSD Card, Anyway?
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, speed matters. And just like with their bigger siblings, SD and Compact Flash cards, the speed of microSD cards vary widely from card to card.
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 HERO7 Black or GoPro HERO6 Black, for instance.
So you really need to look further to 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. The read speed, which is often used in marketing, tells you how fast you can get data off the card. 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," "Extreme," 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. My focus here is on their speed for recording video and burst mode photos.
The Current Top 4 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 video. As you can see in the detailed table below, some models, like the SanDisk Extreme Pro line, have several models that rank amongst the fastest in my tests because the manufacturers reuse the name as they come out with newer, faster cards.
1. Lexar Professional 1800x U3 microSDAmazon
This card is very, 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. This version has the U3 and UHS-II markings on it. The graphic on Lexar's website has it with V90 markings on it, but I haven't come across that version for sale yet.
The second catch is that they're not all that easy to find. Lexar has been going through some corporate upheaval lately, including a change in ownership. I don't know to what extent that has affected manufacturer and supply lines, but the upshot as a customer is that these high-end Lexar cards aren't as readily available as some of the other options here.
A nice perk of this card is that it comes with two readers: a microSD-to-SD adapter cartridge and a USB thumb reader. Both are UHS-II, and the thumb reader in particular is about the fastest I've come across. It also comes with a license to Image Rescue 5 included.
2. SanDisk Extreme PRO V30 microSDAmazon or B&H Photo
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.
3. SanDisk Extreme PLUS U3 microSDAmazon
The Extreme PLUS line of SD cards sits between the Extreme and Extreme Pro in SanDisk's lineup. As with the Extreme Pro, the performance of recent versions has been similar, so you don't necessarily need this very 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 5 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.
4. Samsung EVO U3 MicroSDAmazon or B&H Photo
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.
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|
|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|
|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|
|SanDisk||Extreme PLUS (SDSQXWG)||V30||UHS-I||87.2||91.0||90.3||85.3||95||90|
|Samsung||Pro Select (MB-MF)||U3||UHS-I||85.0||91.7||90.6||84.6||100||90|
|Samsung||EVO Select (MB-ME)||U3||UHS-I||84.4||86.8||82.9||77.0||100||90|
|Samsung||Pro Select (MB-MF)||U3||UHS-I||84.3||93.2||88.6||80.9||100||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|
|FreeTail||Evoke Pro 1000x||V60||UHS-II||70.6||94.4||93.5||16.2||240|
|Samsung||EVO Select (MB-ME)||U3||UHS-I||70.3||91.0||88.1||65.2||100||60|
|SanDisk||Extreme PRO (SDSQXPJ)||U3||UHS-II||68.9||211.5||205.3||13.0||275||100|
|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 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 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 Lexar LRWM05U-7000 USB thumb reader. It's one of the two options that comes with the Lexar 1800x microSD cards. I've found it to be the fastest of the readers that are readily available--faster even than my Lexar Professional Workflow microSD reader--and because it connects directly to the computer's USB port, it eliminates any potential issues with cables or external card reader interfaces. It's connected via USB 3.0 and is UHS-II compatible.
For the software, I'm using the benchmarking suite in Digital Media Doctor by LC-Technology, the company behind SanDisk RescuePro. All cards were new or near-new and freshly formatted. Because it's quite normal for results to vary a bit between tests, I'm running each set of tests three times and averaging the results.
For the computer, I'm using an iMac Retina 5K late-2014 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.
And, finally, the cards themselves. I buy all of these myself through standard retail. I don't accept freebie cards or conduct sponsored tests.
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.
Technically, it's possible to use a computer to format a 32GB card with eXFAT or a 64GB with FAT32, for example, but it's generally not recommended. Some cameras do a check, and if they don't see the filesystem it expects for that size card you'll get an error. And when you format the card in the camera, which is always considered best practice to avoid problems, the camera will format using the filesystem expected by the SD Association specs for that capacity card.
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 simply 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 4K video and faster. 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, and for now, those are pretty rare, but the 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.
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 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. Using a UHS-II card in a camera or host that only supports UHS-I will result in it falling back to UHS-I speeds. 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.
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 actual miniSD cards for sale and you'll be hard-pressed to come across any devices that use them specifically.
MicroSDHC and microSDXC or refer to the 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 spare/s as backup.
- Memory cards are not designed for long-term archival storage of photos and video. 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.
Images and product information from Amazon Product Advertising API were last updated on 2019-04-21 at 10:28.