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

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

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

TL;DR: The Highlights

  • Best Value microSD
  • All-time Value SD card
  • Functioning microSD
    (for Phones / Tablets)
  • Performance microSD
    (for video recording)
  • Performance SD card
  • High Chapters microSD
  • High Capacity SD bill of fare

SD Card Nuts: Size & Storage

All SD cards (short for Secure Digital), regardless of their size, utilize one or ii pocket-size NAND flash retentiveness chips -- similar to those found in USB retentiveness sticks and SSDs -- and a tiny processor to manage the flow of data and instructions.

There are 3 standards for the dimensions, and they are incompatible with each other. In other words, a miniSD card reader won't piece of work with microSD cards (unless y'all utilize an adapter):

  • Standard SD cards: ane.26 x 0.94 ten 0.083 to 0.055 inches (32 x 24 x 2.1-one.iv mm)
  • miniSD cards: 0.85 x 0.79 x 0.055 inches (21.5 x 20 x 1.4 mm)
  • microSD cards: 0.56 ten 0.43 x 0.039 inches (15 10 11 x 1 mm)

Standard SD cards all come with a small locking toggle, that enables/disables the ability to write or delete information on the card; however, mini and microSD cards don't take this feature. In that location'south also a further five categories within the size classes, that betoken the connection system and data chapters of the card:

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

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

SDSC is restricted to FAT12, FAT16, and FAT16B. SDHC is almost always FAT32 and the XC/HC versions use exFAT. The exFAT file format was specifically designed for NAND flash devices and is likely to remain the standard for many more than years.

SDSC, SDHC, and SDXC cards are supported in a broad 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 e'er college resolutions -- only there will ever be an SD carte for everyone's needs and upkeep.

SDUC is yet very new, so it will be some fourth dimension before nosotros see produces routinely supporting it; 128 TB of storage should exist plenty for the majority of users for years to come!

The table above, from the SD Association, shows how the Secure Digital technology has inverse over the past two decades and highlights but how quickly they grew in storage capacity.

You'll probably take as well noticed that there's even more to SD cards than merely capacity: time to talk about performance.

SD Carte Functioning: Speed Classes

All SD cards use the piffling brass contacts at the end of the package to receive and send data, in the grade of instructions and data. The interface between the card and the reading device has evolved with each specification revision -- in some cases, the updated arrangement just runs faster (i.eastward. the bus clock is higher) only in some cases, the SD card has extra contacts to provide more channels for the data.

The differences between all the interfaces and performance are set out in and then-called speed classes, and each 1 is more often than not organized past the peak bus throughput . This is a measure of the maximum amount of bytes per second that tin can be transferred between the SD menu and host device.

A microSD carte du jour sporting an extra row of contacts, for more performance. Epitome: Wikipedia

Still, not all NAND flash chips are the same, so the speed classes too signal the minimum sequential write charge per unit -- the slowest speed at which information can be put onto the memory chip in a structured, rather than a random, way.

With and so many speed classes to go your head effectually, it can be catchy to figure out what rating you really need. In the table beneath, we can come across how they roughly compare.

Speed Classes

Speed Form Min. Seq. Writes (MB/south) UHS Speed Course Video Speed Class Ideal Workload
Class 2 (C2) 2 Standard definition recording and playback
Class iv (C4) iv 720p/1080p video
Form 6 (C6) six Video Class 6 (V6) 720p/1080p, some 4K video
Class x (C10) ten UHS Course ane (U1) Video Class 10 (V10) 720p/1080p/4K video
30 UHS Class 3 (U3) Video Form 30 (V30) 1080p/4K video @ 60/120 fps
sixty Video Class sixty (V60) 8K video @ 60/120 fps
90 Video Class xc (V90) 8K video @ threescore/120 fps

The SD Association came up with the speed nomenclature systems to aid differentiate what cards are all-time suited to what purposes. The simple Class number is the nigh immediate indicator to the speed of an SD card, with Class two (ii MB/s) cards being toward the bottom of the spectrum and are best geared towards less enervating tasks, such as recording standard definition video.

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

Some SDHC and SDXC cards will also support Ultra High Speed (UHS) classification, which offers improved data transfer rates. There are 3 versions of this system and the offset versions to appear (UHS-I and UHS-II) offering two speed modes: U1 and U3. The onetime is essentially the aforementioned as C10, only U3 provides three times greater throughput at 30 MB/south -- expert enough for 4K videos at a high frame rates.

The symbols in the lesser right corner show that this is a UHS-1 U3 microSD card

With SD Specification 5.0, the clan provided another rating organization: Video Speed. This classification is meliorate at carrying its data, with Video Course 10 (V10), for example, applying to cards that have a minimum sequential write speed of 10 MB/southward, through to Video Class xc (V90 = 90 MB/southward). At that speed, the playback and recording of 8K video at threescore to 120 fps becomes feasible.

In 2022, a faster UHS-III was released, which farther improved the performance of the data jitney, and in 2022, the SD Clan announced the SD Express specification -- this version uses upward to 2 PCI Express lanes to provide a huge increase in throughput.

SD Card Charabanc Speeds

Bus arrangement Peak throughput (MB/s) PCI Express type SD card supported
Default speed (DS) 12.v Not used All
High Speed (HS) 25 Not used All
Ultra High Speed I (UHS-I) 50 104 Not used SDHC, SDXC, SDUC only
Ultra High Speed II (UHS-Two) 156 312 Non used SDHC, SDXC, SDUC only
Ultra High Speed Three (UHS-III) 312 624 Not used SDHC, SDXC, SDUC simply
SD Express 985 1969 PCIe iii.1 (x1 or x2 lanes) SDHC, SDXC, SDUC only
SD Limited 1969 3984 PCIe 4.0 (x1 or x2 lanes) SDHC, SDXC, SDUC only

UHS-I cards have but one set of contacts for sending and receive information, and then when running at the higher speed, the charabanc will run in what is chosen Half Duplex mode: the SD bill of fare will only be able to receive or send information, at any i fourth dimension.

The later versions of UHS sport extra contacts, which permits Full Duplex (ship and receive together), both to occur at the same time; however, in UHS-Ii this results in the bus beingness forced to run at the slower speed. UHS-Three and SD Express don't have this trouble, and e'er run Total Duplex.

At this present fourth dimension, 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 because the performance is only unlocked if the device using the card fully supports it. The tabular array below shows how various cards will function in different UHS card readers, and indicates how SD Limited would compare.

Not shown in the very first table is yet some other category rating. The increased use of SD cards in smartphones and tablets, where the additional NAND flash can exist used as working storage, requires more than than merely good throughput.

The power to handle lots of random data instructions (measured in IOPs, input/output operations per second) is fundamental to ensuring consistent system performance, and in 2022 the SD Association created two further standards: Application Class A1 and A2.

Cards rated A1 are capable good for a random read operation 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 also means that the cards offers a sustained sequential write speed equal to that of V10.

Course Min. Seq. Writes Min. Random Read Min. Random Write Ideal Workload
A1 10 MB/s 1500 IOPS 500 IOPS Editing and updating application data, not only storage
A2 x MB/due south 4000 IOPS 2000 IOPS Specialized uses of the above

All of this makes the rating system somewhat of a minefield to navigate, but generally speaking, it can exist cleaved down into 3 uncomplicated categories: general utilise/value for money, best possible performance, and maximum storage capacity.

For example, a smartphone will just demand something from the offset category, whereas a loftier finish photographic camera or video recorder, used past a professional photographer, will want to consider something from the other ii.

What to Purchase

Although this guide should have equipped you lot with the information you need to option your own SD or microSD menu, we went ahead and chose models for the three categories that stood out equally offering the best combination of specification and cost.

Best Value microSD Carte

  • Samsung Evo Plus 64 GB UHS-I U3 - $13 on Amazon
  • Runner upwards: Samsung Evo Select 128 GB UHS-I U3 - $19 on Amazon

All-time Value SD Card

  • SanDisk Farthermost Pro 64 GB SDXC UHS-I - $20 on Amazon (or $36 for 128GB)

You may have noticed Samsung'south dominance in the wink drive market place if you've upgraded your computers with a solid country drive over the years and in that location'southward a skilful adventure that the company's retention chips are in your smartphone. That being the instance, it shouldn't come up as also much of a surprise to encounter a Samsung-branded microSD carte listed here.

For merely $13, the 64 GB Evo Pro (UHS-1, U3) offers 100 MB/s reads and 60 MB/s writes and ships with an SD card adapter. If y'all need more storage, the Evo Select 128 GB touts the same speeds, and information technology's excellent value at simply $19.

In that location are plenty of other alternatives at this price signal, but you should be enlightened than many are U1 cards; they annunciate the aforementioned read speeds as the Samsung cards, but they have much slower writes of merely twenty-thirty MB/s.

Best High Operation microSD Card

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

Best Loftier Performance SD Bill of fare

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

For a wide bulk of users, the best value cards will be fast plenty and volition offer plenty of storage. Withal, for more specialized use (and if top-end performance is required), make sure yous are buying a carte du jour that's correct for the task, and that your device tin can take full advantage of the bill of fare's rating.

If you want fast storage for a smartphone or tablet, you should be more concerned near fast random admission and reading pocket-sized files simultaneously. The $26 SanDisk Extreme 128GB is rated for faster A2 application operation (4000 read and 2000 write IOPS) and lists 160 MB/due south sequential reads with 90 MB/s write speeds.

For picture show recording on drones and video equipment, you want a card with the highest rating (UHS-Two V90) but those are non available in the microSD format. The next best thing, UHS-Two V60 gets yous sustained threescore MB/s read speeds. The Lexar Professional person 1000x 64 GB (UHS-2, U3/V60) is great value at nether $30, only to take full reward of its performance, the card reader must be UHS-II rated. Larger versions of the aforementioned model are also available.

Finally, if you want the best functioning on a device that uses full size SD cards, pinnacle performing SD cards such as Lexar can reach 300 MB/s reads and ameliorate sustained writes in the larger course factor.

Best High Capacity microSD Card

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

Best Loftier Capacity SD Card

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

If you only need the maximum corporeality of storage yous tin get, your options are more limited in the microSD side every bit you might have come to expect. The Lexar Professional 633x SDSC (UHS-1, U3/V10) card might seem expensive at $199, but y'all won't notice anything bigger for the price. However, if you're routinely shooting 4K video, and then you'll welcome the 1 TB capacity. It's non Application Form rated so if you demand better existent-time performance, so you'll have to cede some storage, and drop down to the 512 GB category. There's lots to choose from here, merely nosotros've gone for Lexar again, equally their High Performance 633x models are A2-rated and very reasonable at under $80.

If it has to exist a microSD format, and yous need the highest capacity and storage, and then it volition have to be SanDisk'due south one TB Extreme model (UHS-1, U3/V30, A2) -- it's currently very expensive at $414, and you'll exist better off with the other choices.