If you want to add storage space to a Nintendo Switch, GoPro or Raspberry Pi, you need a microSD card. But while several cards will be fast enough for storing photos, transferring files and the like, some inexpensive options will perform better than others. We recently put more than a dozen models through a range of benchmark tests to help you find the best microSD cards for your data storage needs.
What to look for in a microSD card
Capacity
The first thing to figure out when buying a microSD card is how much space you need. Modern cards are usually available in sizes ranging from 32GB to 512GB, while a handful offer 1TB models as well. 2TB cards are theoretically possible but still in the prototype stage.
For most, a 128GB or 256GB model should be the sweet spot between price and capacity. But if you need more room — say, for stashing a bunch of games on a Steam Deck — a 512GB card could make more sense and often provides a better cost-per-GB ratio. These days, you can find a decent 128GB card for around $15 or less, a decent 256GB card for less than $30 and (with sales) a decent 512GB card could be as little as $40 (though most cost closer to $50 or $60). There’s a starker increase when you go up to 1TB cards, which typically cost around $100.
Note that a microSD card’s performance may differ depending on what capacity you buy. SanDisk says its 128GB Extreme card delivers sequential write speeds up to 90 MB/s, for example, while the higher-capacity models in the same line offer up to 130 MB/s.
When we talk about microSD cards today, we usually refer to cards that use the microSDXC (eXtended Capacity) standard, which have a capacity between 32GB and 2TB. Your device needs to support this for it to work with a microSDXC card. This will almost never be an issue these days, but some older devices (a Nintendo 3DS for instance) are only compatible with microSDHC (High Capacity) cards, which range from 2GB to 32GB.
Read and write speeds
MicroSD cards are primarily judged on their read and write speeds, which are usually measured in megabytes per second (MB/s). Generally speaking, most microSD cards have faster read speeds than write speeds. These metrics can then be broken down into sequential and random performance. Sequential read and write speeds matter when you’re trying to access or save long, constant streams of data, such as opening a large video or copying a big batch of files from a PC. If you want to use a microSD card for media storage, this is particularly important.
Random performance, meanwhile, is about how quickly a card can read and write small files scattered throughout the device. Since random read/write speeds are much lower than sequential ones, storage device makers tend not to advertise them as loudly. But they’re important if you use a card with a gaming device or a single-board computer like the Raspberry Pi, where it often has to rapidly save and access small bits of data in random locations.
Speed ratings
If you look at a microSD card, you’ll see a buffet of numbers, letters and symbols. Most of these refer to the card’s speed class and performance ratings, which are determined by the SD Association.
A card’s Video Speed Class, or V-rating, details its minimum sequential write speed, which is especially important when recording video from a camera. It ranges from V6 to V90. Most of the cards we tested had a V30 rating, so they have a sequential write speed of at least 30 MB/s. This should be enough to support up to 4K video at lower bitrates. Higher-rated V60 and V90 cards are usually better for capturing 8K, but they come at a much higher cost.
The UHS Speed Class, or U-rating, also refers to a card’s minimum sequential write speed. It comes in two varieties: U3, which mandates a minimum of 30 MB/s, and U1, which is rated for 10 MB/s.
The older Speed Class rating overlaps with the other two systems. It’s signified by a C symbol and goes from Class 2 to Class 10, with the number (again) indicating minimum sequential write speed. This rating is less relevant nowadays, but you may still see a “C10” logo on some cards.
The Application Performance spec, marked by an A symbol, is an indicator of random read/write speeds. This is measured in IOPS, or input/output operations per second, rather than MB/s. There are two categories here: A1 cards offer a minimum random read speed of 1,500 IOPS and a minimum random write speed of 500 IOPS, while A2 cards bump those up to 4,000 IOPS and 2,000 IOPS, respectively. Both ratings also guarantee sequential write speeds of at least 10 MB/s.
Most people should look for a card with V30, U3 and A2 ratings. It’s totally possible to get a solid card without those: A U1 card might be worth it if you just need a cheap option with a high capacity to hold files, for example. V60 and V90 cards are worth a look if you’re serious about shooting high-resolution photos and video as well. But generally speaking, cards with the certifications above should provide the best blend of price and performance today.
It’s important to emphasize that these ratings are baselines. Many V30 cards offer significantly higher write speeds than 30 MB/s, for instance, and some A1 cards can outperform some A2 models in practice. The speeds advertised by manufacturers aren’t always 100 percent accurate, either: Sometimes the card will be slower in real-world use, other times it may actually be a bit faster.
UHS bus speeds
The other spec to note is the card’s bus interface. Most microSD cards available today are UHS-I, which have a theoretical maximum speed of 104 MB/s. There are also UHS-II cards, which have an extra row of pins on the back and can reach up to 312 MB/s. (A newer UHS-III standard exists as well but hasn’t seen wide adoption just yet.) These are labeled on the card with a Roman numeral I or II.
The absolute fastest microSD cards right now are UHS-II cards, and they’re usually the ones with V60 or V90 ratings. If you shoot lots of 4K to 8K video or frequently use burst mode to capture ultra high-res photos, the performance gains of a good UHS-II card can save you time.
But these are much more expensive than UHS-I cards: This 128GB model from ProGrade Digital, for example, is a relative bargain at $55. You need a device that’s compatible with the UHS-II interface to see any benefits, too, and as we were putting this guide together, stock for UHS-II cards was spotty. For now, the higher speeds aren’t worth the price premium for the vast majority of people, so we mostly stuck to UHS-I options.
A note on card readers, the Nintendo Switch and Steam Deck
While the UHS-I spec has a theoretical maximum of 104 MB/s, some UHS-I cards can exceed that speed through proprietary extensions. You need a compatible card reader and host device to take advantage of that extra performance, though. If you find a UHS-I card advertising speeds higher than 104 MB/s, this is what’s going on. You can see these limits in action with a Nintendo Switch or Steam Deck: Both of those gaming devices support the UHS-I interface and don’t go beyond its official speed, flattening any sequential gains some cards may have elsewhere. The broader takeaway: Your microSD card will only be as fast as the slowest link in your chain.
Warranty
Many microSD cards are designed to be durable, with protection from water, extreme temperatures, X-rays and drops. Still, in case of catastrophe, a long warranty is always good to have. Many manufacturers offer lifetime limited warranties, though we’ve noticed that “endurance” cards marketed to withstand more hours of writing are usually covered for a much shorter period of time.
Avoiding counterfeits
The memory card market has had a particular problem with scammers selling fake products. To guard against this, only buy from a known brand and a reputable retailer such as Best Buy, B&H Photo or Adorama. If you shop at Amazon, only buy if the shipper and seller is Amazon.com. (Though a handful of users have reported receiving counterfeits even from Amazon directly in the past.) Remember: If a price seems too good to be true, it probably is. Be wary of any retailer offering significantly a lower price than others.
Once you receive a card, check its packaging for any irregularities. You can run benchmark tests like CrystalDiskMark or BlackMagic Disk Speed Test to verify its speeds aren’t drastically lower than what’s advertised (or possible, given its specs). You can also use software that’s designed to verify the true capacity and performance of your card, such as H2testw and FakeFlashTest.
How we tested
We put 12 microSD cards through a series of tests to verify their sequential and random performance. These included benchmarks like CrystalDiskMark, BlackMagic Disk Speed Test, ATTO Disk Benchmark and AJA System Test, as well as a few “real-world” tests. We copied and pasted a small folder of photos about 1.15GB in size to and from each card, then did the same with a larger 12.2GB folder containing multiple file types and subfolders, timing the process each time. We also checked how each card performed on the Steam Deck, downloading games of varying sizes — including Stardew Valley, Aperture Desk Job, Metal Gear Rising: Revengeance and Apex Legends — then timing how long it took to launch each game and load save files.
We used a Kingston USB 3.2 UHS-II reader to test each card on both Windows 11 and macOS Sonoma. For the former, we used an Alienware gaming PC with an Intel Core i9-10900F, Nvidia GeForce RTX 3080 GPU, 32GB of RAM and a 1TB SSD. For the latter, we used a 2021 16-inch MacBook Pro with an Apple M1 Pro chip, 16GB of RAM and a 512GB SSD. To use our card reader on the MacBook, we used
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