How to choose an SD card

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• Forgetting an SD card is today's forgetting to load film in the camera — but today's SD cards can do so much more, from expanding the storage space on a smartphone to stashing a terabyte of files in a device not much bigger than your thumbnail.
• While essential for many devices, buying an SD card isn't always straightforward. There are different names, like SDHC and SDXC, and numbers for speed class and storage all mixed together in a jumble of technical jargon. The best SD card for one device may be overkill for the next, or even incompatible.
• For most devices using standard-size SD cards, the SanDisk Extreme Pro SDHC UHS-I is our pick. Not only is it affordable, but it has a decent balance of speed and durability — enough to handle demanding tasks, like recording 4K video and capturing RAW photos.
• For the best microSD card, we opt for the equally-affordable Samsung EVO Plus. But, if you want to learn more on how to choose an SD card or microSD card in this guide, read on.

• See more: The best SD cards you can buy

For anyone new to the world of hyper-mobile local hardware storage, SD cards are a tiny card (or even technically cartridge format) device with metal contacts that transfer data at surprisingly fast rates, measured in megabytes per second, or MB/s.

Starting out as the future-forward storage method for cameras as far back as the early aughts, SD cards are now used for gaming consoles like the Nintendo Switch and just about every Android phone on the planet — not to mention some streaming boxes and other entertainment devices.

By deciphering an SD card's different features, you can find the right SD card for your device, allowing for maximum performance without overpaying for features you'll never use.

How to choose between SD and microSD

SD cards largely come in two popular sizes, the traditional SD and the microSD. Which one you need depends on your device. A majority of mirrorless cameras, DSLRs and compact cameras use SD cards, while microSDs are used in action cameras, drone cameras, and smartphones.

Most microSD cards come with an adapter — the microSD plugs into the adapter and can then be used with any standard SD card reader. While technically, you can use the adapter with a microSD in a camera that requires a full-sized SD, you probably shouldn't. The adapter can slow down the speed of the card, and it also isn't as well-built.

If you're unsure if you need an SD or a microSD, check the specifications for your device, or locate the SD card slot. A microSD card slot will be slightly smaller than your thumbnail, a traditional SD a bit larger thanur guide to the best SD cards and the best microSD cards you can buy

What's the difference between SDHC and SDXC? Choose a SD card capacity

An SD card is no longer called just an SD — you may see SDHC, SDXC or even SDUC. Those extra letters tacked on the end help categorize the memory card's capacity. SDHC stands for high capacity and these cards come in sizes between 4GB and 32GB. SDXC stands for extended capacity and include cards with enough space for between 64GB and 2TB of data. SDUC holds between 2TB and 128TB of data, which is why you don't see these cards around yet — that's a lot of data.

Most modern cameras can use SD, SDHC, or SDXC interchangeably, but if you have an older camera, that may not always be the case. Devices released after 2008 are typically compatible with SDHC, and most devices launched after 2010 will work with SDXC. The original SD card is compatible with any SD device.

So do you need a low capacity, plain old SD card, a mid-sized SDHC or a SDXC? Most cameras and smartphones today use high megapixel counts and large files — a 2GB SD card would fill up pretty fast. The smaller category is still OK for things like low resolution kids cameras, but for the most part, the choice is between SDHC and SDXC. 

A 32GB capacity is enough to hold around 2,000 16 megapixel images or just under a half an hour of 4K video. That's sufficient for hobbyist photography, and even higher megapixel cameras if you don't mind switching cards often. The higher capacity SDXC is going to be best for high resolution cameras, 4K video, and stashing lots of smartphone data.

Some photographers prefer to use smaller SD cards and change them often, that way if a card is damaged, all the photos aren't lost. Others prefer to put everything on one card, since carrying around multiple cards can increase the odds of misplacing one.

Our recommended high-capacity SD card for most people is Lexar's 1TB Professional 633 UHS-I SDXC. With storage equivalent to a small portable hard drive, this card is ideal for those who shoot a lot, as well as for those who enjoy taking time-lapse photography, uncompressed RAW photos, and even 4K video (although we recommend a faster card for video work). This Lexar card is also one of the more affordable high-capacity SD cards you can find.

Choose a speed

Choosing an SD card is about more than picking the proper type and size — the wrong card speed can slow your camera down, or make you overpay for speed you'll never use. Each SD card has a read and write speed in the specifications, but you can see how fast a card is at a glance by looking at the SD card class.

SD card speeds are categorized in one of three ways: speed class, Ultra High Speed (UHS) class, and video speed class. The first, speed class, covers minimum write speeds of 2 MB/s to 10 MB/s — the class number corresponds to the minimum write speed. A class 10 is the fastest for this designation, while a class 2 is the lowest. This speed category is written on the front of the SD card — the symbol looks like the class number inside of a C.

A UHS speed class categorizes even faster speeds. UHS speed class 1 has a minimum write speed of 10 MB/s, class three has a 30 MB/s minimum write speed. The UHS speed is designated by a symbol that looks like a U with the class number inside it.

The newest speed class, video speed class, is written with a V symbol ahead of the class number. In this category, the class number is equal to the minimum write speed, so a V6 writes at least 6 MB/s, a V90 at least 90MB/s.

You may see one more speed category when shopping for an SD card — the bus speed. While the speed class refers to the minimum speed a card offers, the bus speed indicates the maximum possible speed. Currently, most SD cards have either a UHS-I (up to 104 MB/s) or UHS-II (up to 312 MB/s) bus speed. Faster UHS-III (up to 624 MB/s) and SD Express (up to 985 MB/s) speeds have been standardized, but aren't widely available yet.

The biggest difference is that the UHS-II card has a second row of metal pins at the back. That allows for a faster connection with the camera, allowing those faster speeds. However, because the design of the card is slightly different, not all cameras are compatible with UHS-II. Check your camera's tech specs to make sure it is UHS-II compatible — entry level cameras tend to not offer the compatibility. Some cameras with dual SD card slots are only compatible with UHS-II in one of the slots, not both. (If your camera is older than 2014, no need to check, since compatibility wasn't available in consumer cameras until that year).

So which speed  do you need? That depends on the camera or smartphone you are using. For 8K video, you'll need a V60 or V90. The V60, V30 and UHS 3 are ideal for 4K as well as shooting bursts of RAW images on high megapixel cameras. UHS 1, Class 10 and V10 is good for stills on most DSLRs and mirrorless cameras with megapixel counts in the 20s and 30s as well as HD video. Class 2, Class 4, Class 6 and V6 are best reserved for low resolution devices.

If you're looking for a microSD to expand your smartphone's storage, you want a card with that's at least a Class 10, but preferably a UHS 1 or UHS 3. For running apps — and not just storing files — a UHS 3 card is best. Anything slower will reduce the performance of that app.

If top speed and performance are what you need, our favorites are the Sony SF-G Tough UHS-II and Lexar Professional 1000x UHS-II.

What about brand and build?

Chances are, there's more than one brand of memory card that offers the type, capacity and speed that you need. So how do you decide which brand to use?

First, avoid purchasing the cheap no-name SD cards — these types of cards can increase the odds of losing data to a corrupted card, which turns those few extra bucks saved into a whole lot of cash dumped into data recovery. Stick with the top brands such as SanDisk and Lexar. Brands that make other tech products, such as Sony and Samsung, are a safe bet too.

Besides speed and capacity, as you compare brands, consider the card's durability. Some SD cards are waterproof and dustproof, others make no such claims. If you never plan on taking the microSD out of your smartphone, you probably don't need the more expensive cards designed to withstand the zombie apocalypse. If you are shooting with a waterproof camera, are accident prone, or are simply shooting images that need the most protection possible, opting with a more durable card is a good idea.

Choosing one of the best memory cards will get you high performance storage — but depending on the type of device you are using, you may be paying extra for features that you'll never use. Understanding how to choose an SD card means you'll pick the right memory card for your device every time.

The Sony SF-G-Touch UHS-II is not only fast, but it's waterproof and dust proof, making it the best rugged SD cards we've used. SanDisk's Extreme Pro cards are also very durable.

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