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Buy an SD card: What you Need to Know Before Buying an SD Card

The SD cards are part of everyday life of our technology, and secure your camera or smartphone uses one of these. They began to be habitual a decade ago thanks to their small format and their great capacity, and since then they have become a fundamental part of many gadgets.

Today we will discuss everything you need to know about SD cards, from the different existing formats, that Class denomination that has implications for performance, sizes or formats or the different existing standards. If you want to know more, you just have to continue reading.

Origin of SD cards

The SD cards are one of the many existing memory cards on the market. The best known thanks to its high market presence, its standardization and the prices that have not stopped falling over time.

The SD career began in the 90s, when the SD AssociationSDA, was created , which is the entity in charge of creating and maintaining the standards associated with this type of storage. It is formed by companies such as Toshiba, SanDisk, Samsung, Panasonic, HP, Kingston, Motorola Mobility, Canon, Lexar … and others. As you can see, a large part of the large companies in the technology sector.

In 1999, the first version of the SD standard, called SD Specification, was finalized and they began to arrive on the market. Cards in a very small format, just 3×2 centimeters, which experienced a huge growth thanks in large part to the increase in sales of the first digital cameras too.

SanDisk WiFi

At that time they had capacities that today seem ridiculous, only a few megs, but enough to replace the analogue reels (typically with capacity for 16 or 32 photographs) in the number of images to be stored. As a curious note, the SD Specification 1.0 of the first SD in the market marks a minimum capacity of 1 MB, although the usual models were 16, 32 or 64 MB.

The operation of SD cards has remained unchanged, although of course some aspects have evolved. A plastic housing, typically black, in which there is a small NAND memory circuit, a very simple controller and a set of pins (between 8 and 11, depending on the type of card) for the transmission of information and energy issues.

SD adapters

Adapters, easier impossible

The adapters facilitate the use of a card in multiple devices (image via Wikipedia ).

One of the fundamental keys to the great success of SD cards has been the great simplicity of use, just insert into the respective slot and work. They are also very durable, retrocompatible, small, in many cases really large and economically quite affordable.

Despite being born intimately linked with the first digital cameras on the market, its use has gradually been extended to other devices. In the new smartphones are perfect to expand the many times limited internal capacity, and more recently we have begun to see them in many laptops and tablets, fulfilling a function similar to that of smartphones: add capacity, storage space to complement the internal memory.

Classes of SD cards, how to differentiate them

They look alike, and in fact they can be used for the same thing: they offer a storage capacity on which to write certain data. However, there is a very wide variety of SD cards that have been introduced over time, adapting to new uses. From the most traditional to models with technologies that can sometimes be interesting, such as the SanDisk Eye-Fi that incorporates WiFi for a wireless transfer of photographs.


We will start talking about the different standards that the SDA has been creating in these almost fifteen years. They are commonly called SD, SDHC and SDXC. If we seek to differentiate them we will find different card formats (SD, microSD or the lesser known miniSD), several standards of the official specification (which affect the data bus and the capabilities provided) or a curious name that you know for sure: the so-called Speed Class Rating, which allows us to quickly quantify the performance and possible uses allowed.

We all know them as SD, but in reality it is a set of products in turn made up of several byproducts that have been created as they evolved. All have the same format, but incompatibility problems may occur; the differences are focused on the operating buses (faster) as well as of course the capabilities.

SD logo


1999 1.0 1 MB – 4 GB 12.5-25 MB / s
SD logo


2006 2.0 2 – 32 GB 12.5-104 MB / s
SD logo


2009 3.01 and 4.0 (UHS-I and UHS-II) 32 GB – 2 TB 156-312 MB / s

These are the three standards that the SDA has created to this day, although the existing SD card formats are much more recognizable . We are talking about physical formats, where we also find three products:

SD 32x24x2,1 mm. 2 g.
MINISD 21.5x20x1.4 mm. 0.8 g.
MICRO SD 15x11x1 mm. 0.25 g.

Well known by all. Maybe you do not remember the miniSD, today practically disappeared from the market to the detriment of microSD much more common thanks to its small size.

SanDisk Mobile Ultra microSD

In addition to the standards and formats, SD cards differ in a fundamental aspect: the so-called Speed ​​Class Rating, a mechanism that seeks to provide information on the performance of the card at a glance. We have a total of six categories, which ordered from lowest to highest are the following:

CLASS 2 2 MB / s SD Video
CLASS 4 4 MB / s Video 720p-1080p
CLASS 6 6 MB / s Video 720p-1080p
CLASS 10 10 MB / s 1080p video
UHS-I CLASS 1 10 MB / s Real-time 1080p video
UHS-I CLASS 3 30 MB / s Video 4K / 2160p

In June 2011, version 4.0 of the SD Specification , commonly called UHS-II, was presented and is still starting on the market. They are typically Class 3 cards (that is, they guarantee 30 MB / s) although the most common is that they can reach speeds close to 300 MB / s. An example of these are the SanDisk Extreme Pro that are already beginning to be seen in some distributors, even at very high prices.

Past, present and future storage

Few will doubt that SD cards are a fundamental part of modern technology. There are many devices that use them, either as a fundamental pillar (for example for photo cameras) or as an interesting accessory, to add new possibilities (what we know in smartphones).

An SD card is, after all, a flash memory. Durable, stable and easily transportable with us. Its speed is quite high for the uses we give it, although its performance is not comparable to that offered by other devices based on NAND memory. For example, currently an SD card is typically much lower than a USB memory, not to mention SSDs. However, it is true that with UHS-II there is a tendency to significantly improve the speed of the SD, equaling or even surpassing the performance of many USB sticksand approaching the SSD, although these still have the great advantage of offering buses, interfaces and even much higher controllers.

SD cards are perfect for adding that much needed storage capacity. We said that they are essential in cameras and very important in many smartphones, but in recent years they are also making a dent in tablets, laptops and convertibles , taking advantage of the relative scarce capacity motivated by the use of 64 or 128 GB SSD. For example, in the Microsoft Surface Pro 3 that will soon hit the market, an SD is a perfect companion to not suffer with the space included in the factory.

SD cards on tablets

Increasingly common due to the limited space by default of new equipment. Surface Pro 3 is one of the most interesting

They are perfect to add that capacity many times necessary. Only possibility in cameras, smartphones; in laptops they serve to expand space without great worries, although they will be much slower than any other physical storage device installed.

Needless to say, SD cards will continue to evolve in the coming years. Its implementation in the market is complete, and if there is a memory card format used massively that is without a doubt SD. SD? Micro SD? What capacity to choose? That will depend on what use we are going to give it and what device we are going to connect it to.

About Nick Fury

Hi, I am Nick! Apart from being a loving husband and a father of one, I dedicate myself to manage a company full time. Writing is my passion, I started writing a blog some 10 years ago, now reviving this passion again, I would love to express my views and takes on day to day stuff, hope you guys enjoy! Do share your thoughts.

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