5 mistakes not to make when buying a MicroSD memory card

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Joel Fulleda
5 mistakes not to make when buying a MicroSD memory card

And how to extricate yourself from a tide of acronyms

Whether you need it for your smartphone, for a camera or for some other techno gadget, the purchase of a MicroSD card seems like a pretty simple thing to do, doesn't it? But pay attention to some things.

It is incredibly easy to fall into various traps such as paying too much, having a completely mediocre performance or, worse, that the ticket does not work at all.

So let's take a look at the mistakes to avoid when buying a MicroSD card. 

Do you need a MicroSD? All storage devices can be found here, at the best prices

1) Buy incompatible SD cards

All microSD cards fit into the slots, but this does not mean that they must also work. Exist four different formats, as well as various standards, and these are what determine compatibility.

The three main formats that you will already be familiar with are SD, SDHC, S (o microSD, microSDHC, microSDXC, the small and large format coupons are based on the same characteristics). The fourth format is SDUC, announced in June 2018, which will have to pass some time before it is available on the shelves.

Each format is defined in the SD specification, but does not work in the same way. And therefore, the formats are not backward compatible. You cannot use recent coupons in devices that only support older formats.

The differences between the formats are quite significant:

- microSD: Has a capacity of up to 2GB and works in any microSD slot.

- microSDHC: has a capacity of over 2GB and up to 32GB, and works with any device that supports SDHC and SDXC.

- microSDXC: has a capacity of more than 32 GB and up to 2 TB (although, at the moment, the largest capacity card available on the market is 1 TB), and is only supported in SDXC compatible devices.

- microSDUC: supports cards of up to 128 TB (!) and requires a compatible device.

In addition to checking that the format of a coupon is compatible with the hardware at your disposal, you will also need to check other details. Here are what they are:


First, a device that is equipped with a microSDXC slot does not automatically support any size that is marketed in this format. The Samsung Galaxy S9, for example, it officially supports cards up to 400 GB. There is no guarantee that a 512 card will work.

And if you intend to use your microSD card with your PC (for example, to move files from your mobile) you will also need to make sure that the PC supports the filesystem in which the card was formatted.

MicroSDXCs use the system by default exFAT. Windows has been supporting it for over a decade, MacOS instead only from version 10.6.5 (Snow Leopard).

Ultra High Speed

The SDHC and SDXC formats support Ultra High Speed ​​(UHS) bus interface, which, put simply, allows data to move at much faster speeds. The three versions of UHS are UHS-I (with bus speeds of up to 104 Mbps), UHS-II (up to 312 Mbps) e UHS-III (up to 624 Mbps).

In order to benefit from the best performance of UHS, your hardware must support it. UHS Memory Cards work in older slots but with a reduced bus speed of 25 Mbps.

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2) Choose the wrong speed

Identifying the speed of a microSD card is even more complicated than decrypting formats and compatibilities. There are no less than six methods to understand how fast a coupon is, and it is quite common for manufacturers to exploit them all.

Speed ​​class

The speed class shows the minimum write speed of a memory card in megabytes per second. There are four speed classes, defined as follows: 

- Class 2: At least 2 Mbps

- Class 4: At least 4 Mbps

- Class 6: At least 6 Mbps

- Class 10: At least 10 Mbps

The baseline performance level indication serves to identify whether a bet slip is suitable for a specific task. But since it doesn't say anything about top speeds, it's technically possible for a Class 2 coupon to be faster than a class 6 card. Class 10 cards should always be much faster, as the bus speed is 25 Mbps (compared to 12.5 for classes 2 and 6).

UHS speed class

The UHS speed class shows the minimum write speed of microSD cards that support UHS-I, II and III bus speeds. We place it in a separate category because some manufacturers list both classes on their coupons. The two UHS speed classes are:

- U1: write speed of at least 10 Mbps

- U3: write speed of at least 30 Mbps

Performance class in applications

The performance class in applications indicates a minimum continuous write speed of 10 Mbps, as well as minimum random read and write speeds measured in input / output operations per second (IOPS). This ensures an acceptable level of performance when saving and running Android apps on the Memory Card.

There are two classes:

- A1: minimum random read speed of 1500 IOPS; minimum write speed of 500 IOPS

- A2: minimum random read speed of 4000 IOPS; minimum write speed of 2000 IOPS

Application performance class is a factor to consider when planning to install Android apps on a microSD card. It is not absolutely essential, however, since the coupons without the A classification can have the same performance (if not better).

Video speed class

The video speed class establishes a minimum sequential write speed, which is essential when making videos. The higher the resolution of the video, the more speed you need.

There are 6 classes for videos:

- V6: minimum write speed of 6 Mbps

- V10: minimum write speed of 10 Mbps

- V30: minimum write speed of 30 Mbps

- V60: minimum write speed of 60 Mbps

- V90: minimum write speed of 90 Mbps

Speed ​​classified

While it is generally safe to assume that a higher speed class is associated with better and faster performance, especially in the case of UHS cards, some manufacturers also cite a maximum speed for their products.

These speeds are in megabytes per second and are used to choose the fastest tickets ever. The speeds are based on the manufacturer's tests, however, and therefore can represent a very optimistic scenario compared to what is encountered in daily practice.

In practice, there are other external factors that affect read and write speeds. If you are copying files to your PC, for example, the characteristics of the PC itself play a very important role. Even the USB cable you are using.

Relative speed

The other way producers show the speed of their coupons is back to the days when we all burned CDs. The original transfer speed of CDs was just 150 Kbps. As time went on, burners were advertised as 2x, 4x, 16x and so on, showing how many times they were fast by multiplying multiples of 150 Kbps.

You will often see microSD cards with this type of rating. When a bet slip is described as 100x, it means it is 100x150 Kbps, that is 15 Mbps. That speed, once again, must be understood in ideal laboratory conditions.

3) Choose the wrong SD card for the job you intend to do

When purchasing a microSD card, it is important to choose one that is made specifically for a particular job. This means finding a coupon that is fast enough and roomy, but not necessarily the largest and fastest on the market.

UHS-II U3 ​​coupons often have a very high price tag, and you won't always notice any additional benefits over the others. If you use a microSD card to save apps on your smartphone, purchase one with a rating of Performance class in applications. If, on the other hand, you want a card to shoot 4K video on your smartphone, consider the size and speed as priority.

La SD Card Association recommends UHS Class 3 (U3) or higher cards for 4K video. For Full HD movies, on the other hand, it suggests Class 10 or Class 6. If the writing speed of the card in your possession is too low, the result will be dropped frames and jerky videos.

As far as photography is concerned, some prefer to have several smaller-capacity coupons than to have a single, huge one, to minimize the risk of losing all the photos in case of damage (unlikely event, but always possible).

If you shoot in RAW, where files can be 50 Mb or more, you will benefit from having U1 or U3 cards (at least SDHC).

And in case you were wondering, there is no difference between a full-size card and a microSD card in an SD adapter. If your camera only had an SD slot you could easily use a microSD.

4) Buy fake MicroSD cards

It seems like an obvious thing to avoid, but buying a fake microSD card is an incredibly easy thing to do.

If you find a great deal on memory cards from a seller DON'T reliable, there is a realistic risk that they can be counterfeit. And a few years ago a SanDisk engineer claimed that a third of all memory cards in circulation were fake. That number is unlikely to have declined since then.

There is a page in the eBay buying guides that teaches you to spot counterfeits by the way they are common. The counterfeit coupons correctly report the advertised capacity on the package, but in fact they contain much less. This is something you don't notice until you realize that the bet slip is filling up too quickly.

Even some sellers on Amazon Warehouse have been blamed. If you are going to buy from sources you do not know, read the reviews carefully first. Use the utility H2testw on Windows or F3 for Mac and Linux to verify that the microSD cards you own are genuine.

5) Save on brands

Many will have happened to have flash memory cards that have stopped working for no apparent reason. While reliability is usually excellent, even microSD cards can fail, and when they do, they carry all the data with them.

For this reason, buying coupons from big brands is a much wiser thing than buying coupons from half-known brands to save a few euros. For sure, with a branded card you gain in terms of performance, reliability and sturdiness, since the cards are protected against shocks, water and even against X-rays from airports.

Additionally, manufacturers such as Lexar and SanDisk offer bonuses such as a lifetime warranty and access to image recovery software.

Do you need a MicroSD? All storage devices can be found here, at the best prices


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