Just any old card won’t do though, especially if you’re trying to record HD or 4K video - you need the best microSD card. Here we explain how to choose a card that’s right for your needs and review some of the best microSD cards.
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MicroSD card buying guide
First of all, it’s important to understand microSD standards as well as all the markings. There are different types of microSD card, even if they look identical.
The first is microSDHC. The HC stands for High Capacity is covers sizes from 4-32GB. Above 32GB is microSDXC (XC stands for eXtended Capacity), and the largest card you can currently buy is 256GB. However, the latest phones claim to support microSD cards up to 2TB. Check your device's support before buying a card: many dash cams don't support SDXC, so are limited to 32GB.
There are various standards for speed, and you may see more than one on a card:
- Class x
In each case, x will be a number and the number will tell you how fast the card is at a certain task.
The original speed marking was a number inside the letter C (middle in the image above). The number denoted the minimum sustained write speed, so a ‘Class 6’ card would be capable of writing at 6MB/s – that’s six megabytes per second.
That's a sequential write speed, so it only applies when writing large amounts of data (such as when recording video) in sequential memory cells. It doesn't apply to random 4KB writes, which is the typical use in a phone or tablet when small amounts of data are written to random locations.
Many devices which record HD video demand a Class 10 card, but most Class 10 microSD cards are capable of much more than the minimum of 10MB/s write speed.
This is where the UHS system comes in. It stands for Ultra High Speed, and uses a number in the letter U to denote the class. A UHS class 1 card writes at a minimum of 10MB/s and a UHS class 3 card writes at a minimum of 30MB/s.
You may also see UHS-I or UHS-II on the card. This tells you which technology the card uses. The UHS-I ‘bus’ can operate at up to 104MB/s, while the UHS-II bus can transfer data at up to 312MB/s. This doesn’t mean the card will read and write at those speeds, only the maximums.
In order to benefit from the higher speeds available with a UHS-I or UHS-II microSD card, you’ll need a device that’s compatible with this standard.
You can easily spot a UHS-II card as it has a second row of pins underneath the main set. All the cards on test here are either Class 10 or UHS-I.
V (video) rating
There’s a new speed rating called the Video Class. You’ll start seeing this on cards soon, as a V with a number beside it. Like the original Class system, it denotes the minimum sequential write speed in MB/s and ranges from V6 up to V90.
The SD Association recommends the following classes of card for recording at different video resolutions:
The SD Association has also just announced that cards will start bearing an App Performance Class, which will help buyers identify which cards are suitable for popping into a phone or tablet and using for storing and running apps.
It works in a similar way to the video class, and you'll see an A1 logo on a card which meets the minimum requirements which are:
- Random Read Input-Output access Per Second (IOPS) of 1500
- Write IOPS of 500
- Sustained Sequential performance of 10MB/s.
The logo looks like this:
What is UFS? The new microSD card explained
Confusing things even further, Samsung has unveiled the 'successor' to microSD, known as UFS or Universal Flash Storage. These cards come in 32-, 64-, 128- and 256GB capacity and are much faster (five times faster, in fact) than microSD, with sequential read speeds up to 530 megabytes per second.
Samsung says UFS can read a 5GB full-HD movie in around 10 seconds, whereas it would take a UHS-1 microSD card around 50 seconds.
Write speeds are also lightning-quick, up to 170MB/s. That's almost double the speed of the fastest microSD cards available today.
No technology products available today can accommodate UFS cards, but the technology will be coming in the near future. You should note, though, that microSD and UFS cards are not interchangeable - you must buy the type of card listed in your device's specifications.
Temperature, X-ray and shock-proof
MicroSD cards are tiny and easy to lose, but in addition to buying a carry case for your collection, it’s important to choose cards that will survive travelling and any other factors which threaten their operation.
Some manufacturers state that their cards are water-proof and also x-ray proof. However, these are characteristics of pretty much all microSD cards. Data isn’t stored magnetically, so airport scanners shouldn’t pose a problem, and as long as you’re not trying to read or write data to the card in a non-waterproof card reader underwater, a microSD card should shrug off getting wet.
Cards can also be rated to survive in certain temperatures, say from -25 to 85 degrees Celsius, be ‘shock’ proof and more. As long as you’re not paying more for such cards, there’s no harm in buying one of these cards so that you can claim on the warranty if it fails because it got too hot or was vibrated too much. Quite how you would prove the cause of failure is another matter.
Warranty, therefore, is more important than any of these things: check not only the duration but also the terms but also what it covers.
Which cards to buy
Our recommendation is to stick to the well-known brands which will offer a warranty on their cards. Reputable brands include: Toshiba, Samsung, SanDisk, Lexar, Kingston and Verbatim, among others.
There are plenty of fakes and counterfeit microSD cards, so make sure you buy from a trusted seller. If you see a card on ebay that’s a lot cheaper than you expect it to be, there’s probably a reason!
Before you buy a card, check the maximum capacity of your device. Some are limited to 32GB as they are SDHC, not SDXC. It’s tempting to get a 128GB card for under £30, but it won’t work if your device can’t access it.
Drones / action cameras
If you’re buying storage with the intention of recording 4K video, go for a card that’s UHS-I Class 3 rated. Many also recommend the same if you’re recording 1080p, especially at high frame rates.
It’s hard to buy using specifications, as it’s the small-file transfer speeds which make a difference here. We’ll report on these when we’ve tested the cards.
The requirements are similar to drones and action cameras, but you’ll tend to find dash cams are less demanding when it comes to write speeds. Most manufacturers recommend a Class 10 card or better.
How we test microSD cards
We use CrystalDiskMark to test the read and write speeds of each card. This tests both the sequential speeds (reading and writing large blocks of data) and small-file performance, using 4KB reads and writes.
Tests are carried out on our Intel Core i7-based test rig over USB 3.0. We use the full-size SD adaptors which come with cards and a Lexar Professional USB 3.0 Dual-Slot Reader. If a card comes with its own USB 3.0 adaptor, as with Lexar's own card, we use that instead.
Samsung Evo microSD
Samsung is one of the biggest brands, so you're likely to sway towards buying a Samsung-branded microSD card, especially if you have a Samsung phone. The Evo+ is the faster variety: the plain Evo here is a mid-range UHS-I card that's aimed at phone and tablet use.
The sample we were sent by Ebuyer didn't come with an adaptor in the pack: you're supposed to slot it into your mobile and never need to use it in a full-size SD slot. However MB-MP64DA model does come with one, and there's another version with a USB adaptor.
The Evo has a 10-year warranty, which is one of the longest around.
The packaging boast of "up to 48MB/s Transfer Speed with UHS-I" and we saw a sequential read speed 45.8MB/s (47MB/s dead with zero queue depth) so it's right on the money. Write speeds aren't half bad either: 26.5MB/s in the multi-threaded sequential test and this increased significantly to over 39MB/s with no queue depth.
For phone and tablet use, you're more interested in 4KB performance, and here the Evo shines: it scored 9MB/s when reading and 3MB/s when writing.
This makes it one of the best choices overall, especially if you're sticking it in a phone that's capable of recording 4K video. However, the Evo Plus is only a couple of quid more expensive, is faster and comes with an adaptor. For reference, the Evo (the MB-MP64D version) works out at roughly 20p per GB. It's cheap as chips!
SanDisk Extreme Plus microSD
The Extreme Plus is SanDisk's flagship range of microSD cards, and it certainly doesn't disappoint. It claims up to 95MB/s read speeds and 90MB/s write.
We were impressed when we saw it return over 87MB/s and 85MB/s for reading and writing in CrystalDiskMark. In fact, it went even faster in short queue depth test, with 92MB/s for reads and almost 88MB/s for writes.
That makes it a superb choice for recording video in 4K drones and action cameras, or burst photography in a DSLR. It's also a fine performer for phones and tablets thanks to strong 4KB performance of 9.3MB/s when reading at 4MB/s when writing these tiny files.
It's a fantastic microSD card that's only held back by its high price of over 70p per GB. Unless you need these high speeds, you'll find better value elsewhere.
Kingston microSD Action Camera
Available in 16, 32 and 64GB capacities, the Kingston microSDAC card is designed for action cameras (that's what the AC stands for). It's a UHS class 3 card, which means is must write at a minimum of 30MB/s.
You can buy it with or without the full-size SD adaptor and you'll actually save a few quid by going without.
It wasn't too surprising, given the aim of this card, to see very poor random 4K performance, so don't buy this thinking you'll swap it into a phone or tablet at some point.
No, this card is purely for sticking in your GoPro or drone and recording video. With sequential write speeds of 70MB/s, this card is the third fastest for writing that we've tested, and way faster than the 45MB/s it claims on the packaging. It's also very quick at reading - just under 90MB/s (which is what Kingston claims).
All versions work out at about 50p per GB, which makes it the best-value microSD card for recording 4K or high frame-rate slo-mo video.
Verbatim Pro+ microSD
The Pro+ is a UHS-I Class 3 microSDXC card which claims to read at up to 90MB/s and write up to 80MB/s. It comes with an adaptor which turns it into a full-size SD card.
Our tests showed that our 64GB card it didn't live up to those figures, maxing out at a whisker under 67MB/s for sequential reads, and only 44MB/s for writing. Not the slowest by any means, but some of its rivals (the SanDisk Extreme Plus) got much closer to similar claimed speeds.
It's perfectly adequate for Full HD recording, and also has enough pace for 4K too - but other cards are significantly faster.
For tablet or phone use, it's a mixed bag, managing almost 12MB/s when reading 4KB files - a decent speed, but less than 1MB/s when writing them.
You can find it for less than £30 if you hunt around, but at roughly 50p per GB, it's certainly not the cheapest option.
Lexar Professional 633x microSD
Unlike most microSD cards, Lexar bundles this one with a USB 3.0 dongle rather than a full-size SD adaptor. Interestingly, it's intended to be used in "sports cameras" as well as phones and tablets, and boasts of 95MB/s on the packaging (that's what 633x means = it's 633 * 150KB/s). It's an UHS-I Class 1 card, and it's the one DJI ships with it's Phantom 4 drone.
That 95MB/s is - of course - a read speed, and Lexar doesn't mention a write speed, only stating that it is "lower". We were a bit disappointed then, to find that after managing a great 92MB/s read speed when using the included dongle, it managed only 32.4MB/s when writing sequentially. A *lot* lower, then.
4KB performance wasn't outstanding either: it managed 7.7MB/s when reading and 1.3MB/s writing small files. Without the long queue depth in CrystalDiskMark it went slower still: 7.2MB/s and 0.8MB/s respectively.
It's not all bad news, though. The card is certainly fast enough to record 4K video and it's cheaper than you might expect at about 30p per GB.
Toshiba Exceria M301 microSD
There are different models in the Exceria range, and the M301 is a UHS-I Class 1 card intended for recording up to Full HD video, whether in an action camera or an Android phone. If you're intending to record in 4K, Toshiba recommends the Exceria Pro M401 or M501.
Capacities range up to the 128GB card we've tested here, and you get a full-size SD adaptor in the box.
Toshiba claims up to 48MB/s read speeds, as we saw a shade over 45MB/s in CrystalDiskMark's main sequential test. With no queue depth, it managed 46.6MB/s - a great result. Write speeds weren't so good. The card couldn't quite reach 18MB/s, and was even slower in the basic sequential test at only 10.9MB/s, barely scraping over the minimum required for a Class 10 card.
When it came to 4KB files, the Exceria managed almost 7MB/s reading them and just over 1MB/s writing. These are average among the microSD cards we've tested: only the SanDisk Extreme Plus was significantly faster.
Transcend Ultimate microSD
Transcend's Ultimate range offers good performance and a lifetime warranty, and also uses MLC technology.
It's not cheap: £40 for at 64GB card makes it one of the most expensive here at over 60p per GB. The 32GB version works out cheaper per GB, but only marginally.
The good news is that it almost matched the SanDisk Extreme Plus for sequential read and write speeds: 85.8MB/s and 82.8MB/s respectively.
It couldn't keep up in the 4KB tests, though, averaging 8MB/s when reading and 1.5MB/s for writing. That's quicker than average, but the cheap-as-chips Samsung Evo outperforms it for phone and tablet use.
The Transcend Ultimate is really only a sensible choice if you need the fastest write speeds for high-bitrate 4K recording, where it almost matches the SanDisk card, but at a cheaper price. It's much better value in the US, where it costs less than $40.
PNY Turbo Performance microSD card
PNY’s Turbo Performance microSD card is designed for 4K action cams (or drones) with a claimed 90MB/s speed, although as we found out during our testing, this refers to read speeds rather than write speeds.
Using CrystalDiskMark, we saw fairly decent results with 90.4MB/s read speeds and 62.2MB/s write speeds. The latter is more than enough for recording 4K in consumer cameras, but it's not the fastest we've seen.
But what about for use in smartphones and tablets? With a focus on action cameras, it’s not surprising that its random 4KB performance wasn’t the greatest with read speeds of 7.1MB/s and write speeds of only 0.6MB/s. So don't buy it with a view to sharing it between your action camera and an Android phone.
In terms of price, it works out at 63p per GB for the 32GB version, so it’s noticeably more than the Kingston microSD Action Camera card which also performs slightly better.