Why memory cards are still so useful

Memory cards are a great way to store and transport data, and they remain as popular today as ever. Nowadays, with digital cameras and phones, they are a convenient way to exchange photos and videos quickly and easily with friends and family. Moreover, they are a great way to store large amounts of data when dealing with large files such as music, movies, or applications. In addition, some video game systems require memory cards to play games, and there are other specialized uses such as data logging and record keeping. No matter what the purpose, memory cards are still extremely useful.

External memory cards continue to be of great utility and not only to increase the internal storage capacity of a device, as they are also used to run applications or complete operating systems. In this group the MicroSD cards stand out for their compact size and to them we will dedicate this guide 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 from the need to overcome the chaos of closed, mutually incompatible formats that proliferated at the time. They were standardized by the SDA industry group under the Secure Digital standard after an initial development by the manufacturer SanDisk. This was a great success because these components have been enormously useful.

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

MicroSD memory cards

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


This is the main division of these cards. There are three, although really the only one to be valued is the third one, today supported by all new devices:

  • microSD: 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 in devices that support SDHC and SDXC.
  • microSDXC: These are the most modern and the only reference currently available for purchase. Their capacity ranges from 32 Gbytes to 2 Tbytes, the maximum supported so far, although the new SD Express format that we will talk about later will greatly expand it.


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

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

Maximum throughput – Minimum throughput

These are the maximum and minimum data transfer speeds that microSD cards can achieve and have been extended from the original ones to meet the needs of new applications such as 4K recording. The following sections should be taken into account:

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

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

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

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

The random yield is also defined in the standard and are 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.

Rated speed.. Don’t go away… there is more. Most manufacturers quote the rated speed of their card and it is the maximum speed that in read mode they are capable of achieving, expressed in MB/s.

Relative speed. It corresponds to the original transfer rate increase of the CD format (150 KBps). So, you can 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 (fortunately) are disappearing, but just in case you come across them so you 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 web page.

SD Express: a new level

This is a new specification of the Secure Digital standard that has taken this format to another level in performance and capacity. To this end, the SD Express use the PCIe 3.0 interface and the NVMe v1.3 protocol.protocol, the same as those used by other storage products such as SSDs. Under PCIe, an SD Express achieves data transfer performance that will approach that of the fastest removable cards, Compact Flash cards, which are limited by price to the professional camera market.

In addition to the performance improvement it will also increase storage capacity and potentially reach 128 Tbytes. A real barbarity 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 is already announced with support for two PCIe lanes with an additional row of contacts and PCIe 4.0 transfer rates for a bandwidth that from the initial 985 MB/s will grow to a maximum of 3938 MB/s.

The “Express” bus will also be available for the microSD we are concerned with in this guide. Although it will not reach the performance of the larger SD cards, the bus speed will enable read speeds of 624 Mbytes per second. These Express SD cards can be used for advanced photography and video tasks (handling 8K resolutions and RAW captures), which until now have been reserved for the aforementioned Compact Flash. In terms of data storage and software execution (the most used in consumption), the increase in level will be stratospheric. Let’s hope they reach the market soon.

How to choose the card

The capacity will surely be the first question to evaluate, but not the only one. If your device supports it, the minimum would be 32 Gbytes. From there, up to over the Tbyte barrier you have a wide range to choose from.

As for the performancewill 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 as in a Raspberry Pi where we will need more performance. If we use them in cameras for RAW or 4K then you will have to buy the fastest on the market.

Note also the group of “rugged” cards. They are especially dedicated to professionals or users who need memory cards of high durability and maximum resistanceThe software includes a water, dust or X-ray protection for transport hubs, as well as data recovery software.

You can’t go wrong. All the major vendors offer high reliability, speeds above the minimum and good support, even a lifetime warranty on the best models. Almost all usually include an adapter for use in SD slots and can be connected to USB ports with the appropriate adapter.

MicroSD Memory Cards (Pricing March 2023)

With all of the above in mind we go shopping. It must be said that like all other products based on NAND flash memories the price per GB has come down a lot the last few years and if you don’t need too much capacity there are offers for just a few euros. Generally speaking, the 64, 128 and 256 GB versions are the most cost-effective 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 at up to 100 MB/s with the following capacities and prices:

  • 64 GB for €7.
  • 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, includes an SD adapter and is distributed with the following versions and prices:

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

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

  • 64 GB for €10.
  • 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. Shock, vibration and X-ray resistant. Sold with SD adapter in the following versions and prices:

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

Lexar Play. MicroSDXC UHS-I cards, Class 10, up to 150 MB/s. Sold with SD adapter in the following versions and prices:

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

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

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

Samsung EVO Plus. 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 adapter in the following versions and prices:

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

SanDisk Extreme PRO. A Class 10, U3, V30 and A2 microSDXC with up to 170 MB/s read data transfer and 90 MB/s write data transfer. They are temperature, water, shock and X-ray resistant. They are available with / without SD adapter:

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

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

NoteThis 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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