A Guide to Understanding Different Types of SD Cards

A collection of SD cards

When it comes to digital storage, there are different types of storage technologies used for different types of electronic gadgets. One such storage technology is the SD card. Nowadays, different types of SD cards are used in medium to small-sized electronic devices to store media and raw data. In this guide, we'll explore the features and characteristics of different types of SD cards. It'll give you a fair idea about the type of SD card you should choose for your work. The most common use of SD cards is either use them as extended storage in smartphones or as the primary storage in digital cameras.

A collection of SD cards

These SD cards are generally slower than the primary storage available in a typical electronic device. In other words, their read/write speeds are comparatively slower than the default storage device.

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So, let's take a quick look at the number of available options when it comes to selecting and picking an SD card. Remember, higher-capacity cards are quite expensive, so choose wisely when purchasing one.

1. SDSC (Standard Capacity) Cards

These cards were the ones that started it all giving reliable and portable storage options for gadgets and devices. These cards were generally used in music players and low-budget digital cameras.

The data storage capacity of these cards ranges from 128MB to 2GB.

These cards were and are used in devices where the storage requirement is not that huge. Nowadays, they are generally considered obsolete, but you may still find their use in some of the low-end devices.

2. SDHC (High Capacity) Cards

These were the next-generation cards with a lot more storage capacity when compared to its predecessor. The slots made for these cards are backward compatible to accept SDSC cards as well.

The data storage capacity of these cards ranges from 2GB to 32GB.

It's perfect for storing photos and video files. Most mid-range phones and digital cameras support this SD card—out of the box. I've used this card with some of my earlier smartphone models.

3. SDXC (Extended Capacity) Cards

As the name implies, the storage capacity of these cards was extended by many folds when compared to the older versions. These cards used the exFAT file system.

The data storage capacity of these cards ranges from 32GB to 2TB.

The minimal write speed specified by standard ratings for these cards is at least 90MB/s. Because of its high capacity, one can use an SDXC card for storing high-resolution photos and videos.

4. UHS-I (Ultra High-Speed Class 1) Cards

These were the first SD cards to achieve high read-write speeds which is ideal for storing video stream capture. These cards are popular among videographers and professional photographers.

The data transfer rate of these cards can go up to 170MB/s. Their storage capacity varies depending on the vendor and the model.

SanDisk has its own proprietary UHS-I standard that offers much higher data transfer speeds than its competitors. These cards can store thousands and thousands of MP3 songs.

5. UHS-II (Ultra High-Speed Class 2) Cards

The second generation of SD cards in this category comes with even more storage capacity and much higher data transfer rates. They're fit for storing huge amounts of data in a quick time.

The data transfer rate of these cards can go up to 312MB/s.

A high transfer rate facilitates storing and reading 4K or 8K videos without any significant lag. These cards are backward compatible with UHS-I card slots. These cards use FAT32 or exFAT file systems.

6. UHS-III (Ultra High-Speed Class 3) Cards

With extremely high read/write speeds, these cards are best suited for 4K/8K video recordings through high-end capturing devices. Its card slots are backward compatible with UHS-I and UHS-II cards.

The data transfer rate of these cards can go up to 624MB/s.

It has a quick recovery function that resumes data transfer after the card has been removed and reinserted into the slot. Here's a quick comparison between the UHS class of SD cards.

UHS SD cards comparision table

While purchasing a UHS SD card, make sure your device's card slot support that card. For most users, UHS-I and UHS-II are sufficient for their daily use.

7. Application Performance Class Cards

Apart from sequential data transfer mode, these cards can do random read and write operations at an impressive speed.

Application performance class cards (A1) can do non-sequential data transfers at the speed of 1500 reads/sec and 500 writes/sec. Application performance class cards (A2) can do non-sequential data transfers at the speed of 4000 reads/sec and 2000 writes/sec.

These cards can achieve this random read/write capability by using command queuing and the use of a data cache. Though power loss—before the cache is utilized—can lead to loss of data.

These cards are best suited when you want to run applications—directly from the SD card. These cards give you a much smoother experience while working with apps on a smartphone.


Portable devices require a reliable and cost-effective storage medium and SD cards fulfill that need—perfectly. SD cards come in a variety of formats with different storage capacities and read/write speeds.

While purchasing an SD card for your device, always look for compatibility, your storage requirements, and in some cases, the data transfer speed.