As early as 2015, the world was already snapping over 1 trillion photos per year. On top of this, the demand for 8K video devices continues to grow – not only in the broadcast and film industry, but by consumers as well. There’s one thing related to this we don’t often think about, however. All these amazing pics and videos need to be stored somewhere.

Thanks to the cloud, storage is typically an “out of sight, out of mind” thing for a lot of people. Everything gets backed up for us behind the scenes. While cloud storage is freely offered by many providers, the network fees for uploading large, high-resolution photos and videos can quickly burn through data limits or add up in overage fees. Plus, not all video devices support mobile connections. So you still need portable, fast, high-capacity internal storage on your device to store the video until you decide where the final files will eventually “live” – whether in the cloud or on a home storage device.

The noble SD card lives on

Memory cards can usually be purchased at an affordable price, making them an attractive local storage option. SD (Secure Digital) cards – are used as portable storage in a wide variety of consumer devices – video game consoles, set-top boxes, home security cameras, and VR setups to name a few. Most notably, though, the noble SD card still finds its greater purpose in storing high-quality videos and pictures for people on host devices such as digital cameras, drones, action cams, and smartphones. And because SD cards are so ubiquitous and have been around for decades, they’re easily swappable between devices.

The SD Association – with members such as Kioxia, Panasonic, Canon, Tuxera, and others – is responsible for maintaining the standards related to SD card storage. In 2016, they launched Video Speed Class. This class brought zippy speeds and better performance to SD cards. More recently, the SDA announced the SD Express spec, bringing gigabyte transfer speeds to SD memory cards. But how do these classes compare to others? To help sort things out – and to help make choosing SD cards a bit easier for video recording – we put together this quick guide. Plus, we’ve summed it all up nicely in an infographic for you at the end of this post.

1. Know your type

First things first. You of course need the right physical size for your device. SD cards used to come in three sizes: standard (SD), miniSD, and microSD. SD cards are the largest and have a “cut corner” design. MiniSD cards are lighter and smaller than SD cards. This size is not commonly made or found today since the launch of microSD cards (the smallest SD card of all), however. As a matter of fact, SDUC and SDXC cards, explained below, are not found in mini size at all.

Secondly, you’ll want to get the right amount of memory, or capacity, to meet your needs. The SD specifications developed since the year 2000 have led us to four different capacity standards: SD, SDHC, SDXC, and SDUC. Each standard supports a different capacity, or the amount of data you can store on it. SD offers up to 4 GB, SDHC from 2 to 32 GB, and SDXC can hold up to 2 terabytes. And if you’re going to be doing a lot of 4K and 8K video recording – the SDUC standard can hold up to a whopping 128 TB on a single small card. That said, as of 2023, we’ve yet to see any SDUC cards launched to the market.

You can generally find the supported physical size (standard, micro, mini) and capacity standards (SD, SDHC, SDXC, SDUC) in the user manual for your device.

2. Check your speed

The speed class rating was introduced by the SD Association as a way to quickly provide information about the minimum write performance of SD cards. The idea was to help you decide which card to purchase to meet your specific usage needs. The speed class rating shows the minimum speed of the card, not its actual speed. If two cards have the same class, it doesn’t automatically mean that both cards will perform equally. Manufacturers usually go well above those minimum requirements and offer much higher speeds. In addition, the device using the SD card also plays a part. A card might support writing at 100 MB/s, but the device might not be capable of sending data as fast as it can be written. That’s why it’s important to check SD card compatibility from your device’s user manual or tech specs.

Speed Class – SD cards

The original speed class was simply named “Speed Class” and is designated by the Speed Class Mark (shown in the infographic below). Speed Class simply indicates the card has the minimum write performance to record video. The classes are 2, 4, 6, and 10, which correspond with the minimum write speed in megabytes per second. These classes are used in camcorders, cameras using video mode, dash cams, and smartphones covering video formats up to Full HD.

UHS Speed Class – SD cards

UHS stands for Ultra High Speed and offers high performance on UHS-compatible devices. This speed class is known for very rapid data transfer – up to 312 megabytes per second – from the SD card hardware to the device central processing unit (CPU), otherwise known as bus-interface speed. These classes include UHS 1 (U1) and UHS 3 (U3) and support full HD to 4K video formats. UHS classes are used in UHS-compatible devices such as action cams for real-time broadcasts, large-size HD videos, and high-quality professional HD.

Video Speed Class – SD cards

Cards marked with the “V” speed class offer rapid speeds and superior performance for ultra-high resolution, high-quality videos, and multi-file recording. Multi-file recording refers to video data recorded simultaneously with data from another sensor, like location and altitude data in drones, for example. The Video Speed Classes are V6, V10, V30, V60, and V90, and the numbers correspond with the minimum write speed in megabytes per second. This class supports from HD format up to 8K video in drones, 360-degree cameras, action cams, and VR cameras.

The new “spec” – SD Express

The new speedster on the block is SD Express. First announced in June 2018, then updated in May 2020, the SD Express specification offers the fastest data transfer rates – nearly 4 GB/s! The spec can pull these rapid data transfer speeds using the PCIe Gen 4 interface and NVMe application protocols, commonly found in solid-state drives (SSD). What’s so impressive is that you get the same fast performance as computer storage in a tiny, portable form.

This amazing transfer rate is surely promising for huge 8K video files, where you need faster throughput for rapid data transfers. According to the SD Association, the cards should be very applicable for a variety of video applications, including super-slow motion video, RAW continuous burst mode and 8K video capture and playback, and 360-degree cameras/videos. Despite all the potential, we have yet to see an explosion of SD Express cards on the market – plus devices that support the new spec. Expect to see more of these coming in 2022, however. They’ll have “EX” or “Express” as part of the SD logo.

3. Properly format your SD cards before use

Simply put, formatting is the process of preparing your card for use by an operating system. There are several tools you could use to format your SD Card, including the disk utility apps that come natively on Windows PCs or Macs. But before you just go with the default formatter, consider using the official SD Memory Card Formatter app to do the job – especially if you want the absolute best performance and lifetime. The formatters built-in to your operating systems are rarely tested as rigorously as the SD Memory Card Formatter and may not follow the SD standards and specs as closely. The SD Memory Card Formatter is designed to be the best tool for the job, for virtually every type of user – offering you the highest level of performance and reliability for all of your formatting and reformatting needs.

As it just so happens, Tuxera is the developer of the SD Memory Card Formatter app. In our testing of the SD Memory Card Formatter performance, we found sequential reads were on average 52.5% faster over native OS formatters, plus 3% faster random reads and 61.2% faster random writes. That’s obviously a tremendous advantage for any user, but especially videographers and cameraphiles.

Be aware that if you do format your cards, everything on it is deleted in the process. So if you have anything important stored there, make sure you back it up before you format.

You can find the free SD Memory Card Formatter from the SD Association’s website.

SD Memory Card Formatter

Final thoughts

To recap, not all SD cards are the same: size, capacity, speed, and intended use are the determining factors when deciding between SD cards. Even though cloud storage is in the spotlight, SD cards are an easy and affordable way to get extra storage on your cameras, drones, smartphones, and other video-enabled devices.

UPDATE: This post was originally published in Tuxera’s blog in 2016, and updated with new info in 2022.