If it'southward been a while since yous've bought portable flash retentivity, you might be surprised by the broad availability and affordability of loftier-speed, loftier-capacity microSD and SD cards. Unremarkably used to expand the storage in devices ranging from smartphones to drones, microSD cards are more than ofttimes purchased than any other SD form factors, although full sized cards remain popular amidst professional camera owners.

With this guide, we'll break downward what all the different codes and ratings mean, and offer the best choices for a range of categories.

  • Size & Chapters
  • Speed Classes
  • What to Buy?

TL;DR: The Highlights

  • Best Value microSD
  • Best Value SD menu
  • Functioning microSD
    (for Phones / Tablets)
  • Operation microSD
    (for video recording)
  • Performance SD bill of fare
  • Loftier Capacity microSD
  • High Capacity SD card

SD Card Basics: Size & Storage

All SD cards (brusk for Secure Digital), regardless of their size, employ i or two pocket-sized NAND flash memory chips -- similar to those establish in USB memory sticks and SSDs -- and a tiny processor to manage the catamenia of data and instructions.

There are 3 standards for the dimensions, and they are incompatible with each other. In other words, a miniSD carte du jour reader won't work with microSD cards (unless you use an adapter):

  • Standard SD cards: one.26 x 0.94 x 0.083 to 0.055 inches (32 x 24 x 2.1-i.4 mm)
  • miniSD cards: 0.85 x 0.79 x 0.055 inches (21.5 10 twenty ten one.four mm)
  • microSD cards: 0.56 ten 0.43 10 0.039 inches (15 x eleven ten 1 mm)

Standard SD cards all come up with a small locking toggle, that enables/disables the power to write or delete data on the card; however, mini and microSD cards don't accept this characteristic. There's too a further 5 categories within the size classes, that indicate the connection system and data capacity of the bill of fare:

  • SD or SDSC (Secure Digital Standard Capacity): maximum storage of 2 GB
  • SDHC (Secure Digital High Capacity): More than 2 to 32 GB of storage
  • SDXC (Secure Digital Extended Capacity): More than 32 GB to 2 TB of storage
  • SDUC (Secure Digital Ultra Capacity): More than than 2 to 128 TB of storage

The 5th category, Secure Digital Input Output (SDIO), are special in that they contain more than merely storage. These cards sport an extra device that provides additional functions, such as a Bluetooth or GPS receiver. Considering there is a big difference in the storage sizes, each category besides has restrictions of the file format used.

SDSC is restricted to FAT12, FAT16, and FAT16B. SDHC is nearly e'er FAT32 and the Ninety/HC versions use exFAT. The exFAT file format was specifically designed for NAND wink devices and is likely to remain the standard for many more years.

SDSC, SDHC, and SDXC cards are supported in a wide range of devices, such as laptops, smartphones, drones, and digital cameras. The need for increased storage continually grows, thanks to bigger games, more complex apps, and cameras sporting ever higher resolutions -- but there volition always be an SD carte du jour for everyone's needs and budget.

SDUC is nonetheless very new, so it will be some time before nosotros run into produces routinely supporting it; 128 TB of storage should be enough for the majority of users for years to come!

The table to a higher place, from the SD Clan, shows how the Secure Digital engineering science has changed over the past ii decades and highlights but how apace they grew in storage capacity.

You lot'll probably have too noticed that in that location's even more to SD cards than but capacity: time to talk nearly performance.

SD Bill of fare Operation: Speed Classes

All SD cards employ the piffling brass contacts at the stop of the package to receive and transport data, in the form of instructions and information. The interface between the card and the reading device has evolved with each specification revision -- in some cases, the updated system merely runs faster (i.east. the motorbus clock is college) but in some cases, the SD bill of fare has extra contacts to provide more channels for the data.

The differences between all the interfaces and performance are set out in then-chosen speed classes, and each i is generally organized by the peak bus throughput . This is a measure of the maximum amount of bytes per second that can exist transferred betwixt the SD card and host device.

A microSD bill of fare sporting an extra row of contacts, for more than performance. Image: Wikipedia

However, not all NAND flash fries are the same, so the speed classes besides indicate the minimum sequential write rate -- the slowest speed at which data tin can be put onto the memory fleck in a structured, rather than a random, way.

With so many speed classes to get your head effectually, it can exist catchy to effigy out what rating you really need. In the table below, we can run across how they roughly compare.

Speed Classes

Speed Class Min. Seq. Writes (MB/s) UHS Speed Class Video Speed Class Ideal Workload
Class 2 (C2) ii Standard definition recording and playback
Form iv (C4) four 720p/1080p video
Course half-dozen (C6) 6 Video Form half dozen (V6) 720p/1080p, some 4K video
Class 10 (C10) ten UHS Grade 1 (U1) Video Form 10 (V10) 720p/1080p/4K video
30 UHS Class 3 (U3) Video Class 30 (V30) 1080p/4K video @ 60/120 fps
60 Video Class lx (V60) 8K video @ lx/120 fps
90 Video Class ninety (V90) 8K video @ threescore/120 fps

The SD Association came up with the speed nomenclature systems to help differentiate what cards are best suited to what purposes. The simple Grade number is the most immediate indicator to the speed of an SD card, with Grade ii (2 MB/s) cards being toward the bottom of the spectrum and are best geared towards less demanding tasks, such equally recording standard definition video.

At the other terminate of the scale, Course 10 (10 MB/s) cards are capable of recording or playing up to 4K video, although not at a very high frame rate.

Some SDHC and SDXC cards will besides support Ultra High Speed (UHS) classification, which offers improved information transfer rates. There are three versions of this system and the first versions to appear (UHS-I and UHS-II) offer two speed modes: U1 and U3. The quondam is essentially the same every bit C10, merely U3 provides three times greater throughput at 30 MB/s -- good enough for 4K videos at a high frame rates.

The symbols in the bottom right corner prove that this is a UHS-1 U3 microSD bill of fare

With SD Specification 5.0, the clan provided another rating system: Video Speed. This classification is better at carrying its information, with Video Class x (V10), for example, applying to cards that have a minimum sequential write speed of 10 MB/south, through to Video Form 90 (V90 = 90 MB/south). At that speed, the playback and recording of 8K video at 60 to 120 fps becomes viable.

In 2017, a faster UHS-Three was released, which farther improved the performance of the information bus, and in 2018, the SD Clan announced the SD Express specification -- this version uses up to 2 PCI Limited lanes to provide a huge increase in throughput.

SD Bill of fare Omnibus Speeds

Bus system Peak throughput (MB/south) PCI Express type SD card supported
Default speed (DS) 12.5 Not used All
High Speed (HS) 25 Not used All
Ultra High Speed I (UHS-I) l 104 Not used SDHC, SDXC, SDUC only
Ultra High Speed Ii (UHS-II) 156 312 Not used SDHC, SDXC, SDUC only
Ultra Loftier Speed Iii (UHS-III) 312 624 Not used SDHC, SDXC, SDUC only
SD Express 985 1969 PCIe 3.1 (x1 or x2 lanes) SDHC, SDXC, SDUC only
SD Express 1969 3984 PCIe 4.0 (x1 or x2 lanes) SDHC, SDXC, SDUC only

UHS-I cards accept just one fix of contacts for sending and receive information, so when running at the higher speed, the bus will run in what is chosen Half Duplex mode: the SD card will only be able to receive or ship data, at any one time.

The later versions of UHS sport extra contacts, which permits Full Duplex (send and receive together), both to occur at the same time; notwithstanding, in UHS-II this results in the bus being forced to run at the slower speed. UHS-Three and SD Express don't have this problem, and always run Total Duplex.

At this present time, SD cards utilizing UHS-III or SD Express aren't anywhere to be seen on the market, despite the technologies being available for several years. But this is considering the operation is only unlocked if the device using the card fully supports it. The table below shows how diverse cards will role in different UHS card readers, and indicates how SD Limited would compare.

Not shown in the very first table is notwithstanding some other category rating. The increased utilize of SD cards in smartphones and tablets, where the additional NAND flash can be used every bit working storage, requires more than than but good throughput.

The ability to handle lots of random data instructions (measured in IOPs, input/output operations per second) is key to ensuring consistent system functioning, and in 2015 the SD Association created ii farther standards: Application Class A1 and A2.

Cards rated A1 are capable skilful for a random read performance of 1500 IOPS and random writes of 500 IOPS, while A2 significantly increases that, although this does require very specific hardware support. Additionally, the A1/A2 rating as well means that the cards offers a sustained sequential write speed equal to that of V10.

Class Min. Seq. Writes Min. Random Read Min. Random Write Platonic Workload
A1 ten MB/s 1500 IOPS 500 IOPS Editing and updating application data, not just storage
A2 10 MB/s 4000 IOPS 2000 IOPS Specialized uses of the above

All of this makes the rating arrangement somewhat of a minefield to navigate, but mostly speaking, it tin be broken down into 3 simple categories: general use/value for coin, best possible performance, and maximum storage chapters.

For example, a smartphone will only demand something from the kickoff category, whereas a high end photographic camera or video recorder, used by a professional photographer, will desire to consider something from the other two.

What to Purchase

Although this guide should take equipped y'all with the information y'all need to pick your own SD or microSD card, we went ahead and chose models for the three categories that stood out equally offer the best combination of specification and cost.

Best Value microSD Carte du jour

  • Samsung Evo Plus 64 GB UHS-I U3 - $thirteen on Amazon
  • Runner up: Samsung Evo Select 128 GB UHS-I U3 - $nineteen on Amazon

Best Value SD Card

  • SanDisk Farthermost Pro 64 GB SDXC UHS-I - $twenty on Amazon (or $36 for 128GB)

Yous may have noticed Samsung'due south dominance in the flash drive marketplace if yous've upgraded your computers with a solid land drive over the years and there's a expert take chances that the company's retentivity chips are in your smartphone. That existence the example, information technology shouldn't come as as well much of a surprise to meet a Samsung-branded microSD card listed here.

For only $xiii, the 64 GB Evo Pro (UHS-1, U3) offers 100 MB/s reads and 60 MB/south writes and ships with an SD card adapter. If yous demand more storage, the Evo Select 128 GB touts the same speeds, and it'south excellent value at just $xix.

At that place are plenty of other alternatives at this price point, but you should be aware than many are U1 cards; they annunciate the aforementioned read speeds equally the Samsung cards, but they have much slower writes of only 20-30 MB/s.

All-time High Functioning microSD Carte

  • Smartphone/Tablet use: SanDisk Extreme 128 GB UHS-I U3/V30 A2 - $26 on Amazon
  • Video recording: Lexar Professional 1000x 64 GB UHS-2 U3/V60 - $28 on Amazon

Best High Functioning SD Carte du jour

  • Lexar Professional 2000x 64 GB SDXC UHS-II - $83 on Amazon

For a wide majority of users, the best value cards will be fast enough and will offer plenty of storage. However, for more than specialized use (and if pinnacle-end functioning is required), brand sure y'all are ownership a card that's right for the task, and that your device tin can accept total advantage of the card's rating.

If yous desire fast storage for a smartphone or tablet, yous should be more concerned nigh fast random access and reading small-scale files simultaneously. The $26 SanDisk Extreme 128GB is rated for faster A2 awarding operation (4000 read and 2000 write IOPS) and lists 160 MB/due south sequential reads with 90 MB/south write speeds.

For movie recording on drones and video equipment, you want a bill of fare with the highest rating (UHS-II V90) only those are non bachelor in the microSD format. The next best thing, UHS-Two V60 gets y'all sustained 60 MB/s read speeds. The Lexar Professional 1000x 64 GB (UHS-2, U3/V60) is great value at under $30, only to have total advantage of its performance, the card reader must be UHS-Two rated. Larger versions of the same model are also bachelor.

Finally, if you lot want the best operation on a device that uses full size SD cards, top performing SD cards such as Lexar tin attain 300 MB/s reads and better sustained writes in the larger form gene.

Best High Capacity microSD Card

  • More storage: Lexar Professional 633x i TB UHS-one U3/V30 - $199 on Amazon
  • Speed and Storage: Lexar 633x 512 GB UHS-1 U3/V30 A2 - $78 on Amazon

All-time High Capacity SD Card

  • More storage: SanDisk Extreme Pro 1 TB SDXC UHS-I - $354 on Amazon
  • Storage and Value: Lexar Professional 633x one TB SDXC UHS-I - $249 on Amazon

If you simply need the maximum amount of storage you tin can get, your options are more limited in the microSD side as you might have come to expect. The Lexar Professional 633x SDSC (UHS-one, U3/V10) card might seem expensive at $199, just you won't detect anything bigger for the price. Still, if y'all're routinely shooting 4K video, and so you'll welcome the 1 TB capacity. It's not Application Class rated so if you need ameliorate real-time performance, and then you'll have to cede some storage, and drop down to the 512 GB category. At that place's lots to choose from hither, but we've gone for Lexar once again, as their High Functioning 633x models are A2-rated and very reasonable at under $80.

If information technology has to be a microSD format, and you lot need the highest capacity and storage, then information technology will accept to be SanDisk's 1 TB Farthermost model (UHS-1, U3/V30, A2) -- it's currently very expensive at $414, and you'll be ameliorate off with the other choices.