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What microSD card to buy? We explain what is the best


Buying a microSD card for our smartphone is always a good idea, so we can store data in both internal and external memory. Now, with such a variety of memory cards, more than one can mess up. Do not worry! Today we help you make the right choice.

The beginnings of the SD card

SD means Secure Digital and refers to a card format invented by Panasonic, but has been developed together with SanDisk and Toshiba Corporation through the association founded in 2000. The SD Card Association was created with the aim of establishing the standards of these memory cards for better use in portable devices.

SD cards began to reach the general public in 2001, mainly using digital cameras, mobile phones, laptops, game consoles, PDAs … By combining a small size (32 x 24 x 2.1 mm) with good resistance they have become a very practical instrument to store data.

There are different models depending on their size: SD, miniSD or microSD. The latter is the smallest and the one commonly used in smartphones. Then other variables come into play, such as its class and its version. The class is indicated by a number (2, 4, 6 or 10) within a letter “C” (Class) or a number (1 or 3) within a letter “U” (UHS), each with different speeds . Its version is defined by acronyms, SDSC (standard capacity), SDHC (high capacity), SDXC (exstended capacity) and SDIO (Input / Output).

Types of microSD cards

It is simply an SD card in its smallest size (15 x 11 x 1 mm) and, therefore, ideal for smartphones and other small electronic devices. Its capacity varies between 128 MB and 128 GB. But the really important thing is the speed at which the data can transmit.


The initials HC refer to “High Capacity”, of the English high capacity. They appeared in 2006 as the second generation (after the SDSC) and have a capacity of up to 32 GB. Its file system has a FAT32 format, which means that the maximum file size that can be saved is 4 GB.


In this case XC refers to “Extended Capacity”, that is, extended capacity. It was developed due to the need to have more storage since the previous technology was very limited. It began its journey in 2009. This type reaches a storage of 2 TB (2048 GB), but in microSD only up to 200 GB. It has an exFAT format, which means you can save files larger than 4 GB. As a curiosity I will tell you that the maximum theoretical size of a file for this format is 128 PetaBytes (134,217,728 GB). They are the most used today.

Speeds and class

The micro SD cards usually have a number, apart from the gigas, and that gives us information about the speed of data transfer, is the so-called class. This is a very important value even more than the capacity. The number enclosing a “C” takes the pairs of 2, 4, 6 or 10 and that of the “U” only has 1 or 3. It corresponds to the guaranteed minimum transfer speed supported by the SDHC or SDXC cards.

For example, 2 means that it works at a minimum of 2 MB per second, class 4 at least 4 MB / s, and so on. In class U1 the speed is 10 MB / s and in U3 it is 30 MB / s. In daily use on Android was enough with a class 6, although if your terminal is capable of recording video at 4K or you have a device with Marshmallow it is better to opt for class 10 (U1) or directly to a U3.

Speeds for SD cards

Categoria/ Class Velocidad mínima de transmisión Nivel de velocidad Recomendación de uso
UHS 3 30 MB/s Máxima Grabación de vídeo 4K y 2K
UHS 1 / Class 10 10 MB/s Alta Grabación de vídeo HD, Full HD y rafa de fotos
Class 6 6 MB/s Media Grabación de vídeo HD, Full HD
Class 4 4 MB Baja Grabación de vídeo HD
Class 2 2 MB/s Baja Grabación de vídeo HQ

What micro SD card to buy

The main factor to take into account is the memory capacity for the microSD that our smartphone supports. We can know this in the specifications of the terminal. Once this information is known, it will be best to buy the card with the highest possible class to improve the speed when saving or reading data. In short, the best card for us is:

Choose maximum capacity (depending on the device, but surely more than 32 GB). The brand does not matter much as long as you stay among the most reliable (SanDisk, Kingston, Samsung …).

Also choose the maximum possible speed, as long as you get the money (recommended from Class10 onwards).

How to use an SD card

It is quite simple. We just have to insert the card in the specific slot of our smartphone and wait until the device recognizes it. It is advisable to insert and remove the card with the smartphone turned off. Do not ever try to force entry, you can only enter in one position.

In our SD card we can store data, images, applications and any data, also from Android Marshmallow there is native support for microSD card.