Why memory cards are still so useful

External memory cards are still very useful and not only to increase the capacity of a device’s internal storage, since they are also used to run applications or entire operating systems. In this group, MicroSDs stand out for their compact size and we are going to dedicate this guide to them where we will detail all the features that a user should knowending with a selection of the best offers available.

Modern memory card standards were born two decades ago out of the need to overcome the chaos of closed and incompatible formats that were proliferating at the time. They were standardized by the SDA industrial group under the Secure Digital standard after initial development by the manufacturer SanDisk. It was a success because these components have been enormously useful.

Although a part of mobile manufacturers have reduced their support, they are still a essential product group to increase the storage capacity of hundreds of millions of devices (supported mobile phones, tablets, cameras, drones, GPS or portable consoles), in addition to being the essential means to run operating systems on single-board computers such as the Raspberry Pi or to run Android apps and thus free up space on your smartphone.

MicroSD memory cards

They are the smallest in size among all SD, with some extremely small dimensions of 15×11×1 mm, an area of ​​165 mm2 and a practically negligible weight. Surely its size has been key to increasing its adoption. And their versatility is enormous, since they can be used directly on devices that have support for them, through internal SD adapters and also on other external ones, for example when using special flash drives that have microSD readers and are connected to USB ports.

Although externally microSD cards are identical, there is a big difference between them and not only in storage capacity. As with other standards (see USB or Wi-Fi) those responsible have been adding a large number of features that should be known. We are going to review them all because they can be a real gibberish for the general public.


It is the main division of these cards. There are three, although really the only one to assess is the third, now supported by all new devices:

  • micro SD: The oldest. They have a capacity of up to 2 Gbytes and can be used in any microSD slot.
  • microSDHC: They have a capacity from 2 to 32 GB and can be used on devices that support SDHC and SDXC.
  • microSDXC: They are the most modern and the only purchase reference currently. Its capacity goes from 32 Gbytes to 2 Tbytes, the maximum supported up to now, although the new SD Express format that we will talk about later will greatly expand it.


The microSD memory card ecosystem is so huge that when choosing the card we also have to take into account that the performance is sufficient for the use for which we are going to allocate it. This “Class” defines the minimum speed in Megabytes per second which in write mode is capable of supporting the card. The minimum writing speed supported for each class is:

  • Class 2: At least 2MBps.
  • Class 4: At least 4MBps.
  • Class 6: At least 6MBps.
  • Class 10: At least 10MBps.

Maximum – Minimum Performance

This is the maximum and minimum speed that microSD can reach in data transfer and they have been expanding from the originals to cover the needs of new applications such as 4K recording. To take into account the following sections:

The maximum reading speed (sequential) that a card supports is defined by the Ultra High Speed ​​(UHS) specification and has two versions:

  • UHS-Iwith bus speeds of up to 104 Mbps
  • UHS-II with bus speeds up to 312 Mbps

The minimum writing speed (sequential) supported is defined separately, with the numbers 1 or 3 inserted in a U and with two versions:

  • U1: At least 10MBps.
  • U3: At least 30MBps.

He random performance It is also defined in the standard and is offered in two versions:

  • A1: the original
  • A2: new specification that quadruples the minimum in random reads/writes (4,000/2,000 IOPS) of the previous one.

Nominal speed. Don’t go… there’s more. Most manufacturers quote the nominal speed of their card and it is the maximum that they are capable of reaching in reading mode, expressed in MB/s.

relative speed. This corresponds to the original transfer speed increase of the CD format (150 KBps). So, you might see something like “2x”, 4x” and so on. A “100x” would correspond to a speed of 15 MBps.

These last two features are not standardized, they are only used by some manufacturers and (thankfully) they are disappearing, but in case you come across them to know what they mean. The rest of the specifications are usually included and you will see them printed on the cards themselves, on the packaging where they are sold and on the product’s website.

SD Express: a new level

It is a new specification of the Secure Digital standard that has taken this format to another level in performance and capacity. For this, the SD Express uses the PCIe 3.0 interface and the NVMe v1.3 protocol, the same ones used by other storage products such as SSDs. Under PCIe, an SD Express reaches a performance in data transfer that will be close to what the fastest removable cards offer, the Compact Flash that by price are limited to the professional camera market.

In addition to the performance improvement, the storage capacity will also increase and potentially reach 128 Tbytes. A real outrage for SD Express cards that will initially be offered in SDUC, SDXC and SDHC formats. SDA has continued to work on this standard and version 8 has already been announced with support for two PCIe lanes with an additional row of contacts and PCIe 4.0 transfer rates for a bandwidth that will grow from the initial 985 MB/s to a maximum of 3938MB/s.

The “Express” bus will also be available for the microSD that concerns us in this guide. Although it won’t match the performance of the larger SDs, the bus speed will allow it to offer read speeds of 624 Mbytes per second. These SD Express can be used in advanced photography and video tasks (management of 8K resolutions and RAW captures) until now reserved for the aforementioned Compact Flash. As for data storage and software execution (the most used in consumption) its level increase will be stratospheric. Let’s hope they hit the market soon.

How to choose the card

The ability It will surely be the first issue to assess, not the only one. If your device supports the minimum, we would put it at 32 Gbytes. From there, until you overcome the Tbyte barrier, you have a wide range to choose from.

As for the performanceIt will depend a lot on the device where you are going to use it. It has nothing to do with a GPS where we only need to extend the internal storage and little more than if we use it to run applications from a smartphone or an operating system such as a Raspberry Pi where we do need more performance. If we use them in RAW or 4K cameras, then you will have to buy the fastest ones on the market.

Also note the group of “resistant” cards. They are especially dedicated to professionals or users who need memory cards of high durability and maximum resistanceprotection against water, dust or X-rays of transport centers, in addition to including data recovery software.

You will not go wrong. All the big providers offer great reliability, speeds above the established minimum and good support, even a lifetime guarantee on the best models. Almost all of them usually include an adapter for use in SD slots and can be connected to USB ports with the corresponding adapter.

MicroSD memory cards (Prices March 2023)

With all of the above in mind we go shopping. It must be said that like the rest of the products based on NAND flash memories the price per GB has dropped a lot the last few years and if you do not need too much capacity there is an offer for only a few euros. In general, the 64, 128 and 256 GB versions are the most profitable in price per GB. If your device supports it, they would be the preferred choice. We leave you with a selection of current offers.

Kioxia Exceria. The former Toshiba memory brand markets these MicroSDXC UHS-I, U1 cards with up to 100 MB/s with the following capacities and prices:

  • 64 GB for 7 euros.
  • 128 GB for 16 euros.
  • 256 GB for 36 euros.

SanDisk Ultra. microSDHC cards with read speed up to 120 MB/s. Class 10, U1 and A1, include an adapter for SD and are distributed with the following versions and prices:

  • 256 GB for 32 euros.
  • 512 GB for 63 euros.
  • 1TB for 143 euros.

Samsung EVO Select. MicroSDXC UHS-I, Class 10, U1 cards up to 130 MB/s. They are resistant and are sold with an SD adapter in the following versions and prices:

  • 64 GB for 10 euros.
  • 128 GB for 18 euros.
  • 256 GB for 29 euros
  • 512 GB for 55 euros.

Kingston Canvas Select Plus. MicroSDXC UHS-I, Class 10, U3, A1 cards up to 100 MB/s. They are resistant to shock, vibration and X-ray proof. It is sold with an SD adapter in the following versions and prices:

  • 64 GB for 5 euros.
  • 128 GB for 10 euros.
  • 256 GB for 21 euros.
  • 512 GB for 45 euros.

LexarPlay. MicroSDXC UHS-I cards, Class 10, up to 150 MB/s. It is sold with an SD adapter in the following versions and prices:

  • 128 GB for 14 euros.
  • 256 GB for 28 euros.
  • 512 GB for 66 euros.
  • 1TB for 159 euros.

Kioxia Exceria Plus. MicroSDXC UHS-I, Speed ​​Class U3 (V30) for 4K video recording and playback with read speeds up to 100MB/s and write speeds up to 85MB/s.

  • 32 GB for 13 euros.
  • 64 GB for 20 euros.
  • 128 GB for 26 euros.
  • 256 GB for 48 euros.

Samsung EVOPlus. MicroSDXC UHS-I, A2, class 10 memory cards up to 130 MB/s. They are resistant against water, temperature or X-rays, and are sold with an adapter in the following versions and prices:

  • 64 GB for 13 euros.
  • 256 GB for 30 euros.
  • 512 GB for 56 euros.

SanDisk Extreme PRO. Some microSDXC Class 10, U3, V30 and A2 with data transfer in reading of up to 170 MB/s and 90 MB/s in writing. They are resistant to temperatures, water, shock and X-rays. They are marketed with / without SD adapter:

  • 64 GB for 22 euros.
  • 128 GB for 36 euros.
  • 256 GB for 57 euros.
  • 512 GB for 104 euros.
  • 1TB for 202 euros.

Our leading retailers have selected cards for sale and many others that you can

Note: This selection contains links from our affiliates, but none of the products included have been proposed or recommended by them or their manufacturers, but chosen at our own discretion.

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