UHS-I vs UHS-II on microSD & SD Cards

If you’ve looked at buying an SD or microSD card lately, you might have run into some new codes: specifically, UHS-II.

It refers to something called ultra high-speed bus, which in turn refers to the interface between the card and the device. So far, there is UHS-I and UHS-II. There is a specification of UHS-III, but I’ve not seen any cards actually turn up using that yet.

UHS-II is the newer, and potentially faster, system but adoption is still not widespread. And a UHS-II isn’t necessarily guaranteed to be faster than every UHS-I card in practice. While it wasn’t always true initially, the current fastest SD cards are UHS-II (when used with a UHS-II compatible host, that is).

Compatibility

The UHS-I and UHS-II specifications are designed to be backward compatible. That means that you can use a UHS-II card in a device that’s compatible with UHS-I and vice versa. But if you do so, you’ll be limited to the lower spec, in this case UHS-I. That is the general intention, at least. But it gets a little more complicated, because there are different implementations of UHS-I that have different speeds. Some cards fall back to a slower UHS-I spec; better cards fall back gracefully to a UHS-I spec known as SDR104. Unfortunately, that particular part of the card’s capabilities is rarely specified in either the packaging or the technical specs.

But in many cases, it frankly doesn’t matter which you get. But that’s simply because the cameras and devices that can take full advantage of UHS-II are only just starting to become available.

And some that are UHS-II compatible can be a bit quirky. For instance, the FujiFilm X-Pro 2 camera has two SD slots. But only one uses UHS-II. So if you put a UHS-II SD card in the slot that has the UHS-I interface, you’ll be limited to UHS-I speeds.

But if you have a device that does use the UHS-II interface–and the technical specs or instruction manual will say so if it does–then there’s a good chance you’ll get better performance out of a UHS-II card.

One common device where this can become an issue is with memory card readers. Most of the card readers currently available support UHS-I cards. UHS-II cards will work, but they’ll be limited to UHS-I speeds. There are some card readers that do support UHS-II, such as the Lexar SR2 reader or the SanDisk Extreme Pro reader, but you can’t assume that every card reader does.

How to Tell the Difference Between UHS-I and UHS-II

There are two ways to tell the difference. The first is obvious: look at the label or packaging. They’ll have either UHS-I or UHS-II, or sometimes just I or II. Technically, it should be Roman numerals, but you’ll sometimes see it incorrectly written as a number 1, like UHS-1.

You can also tell them apart by looking at the cards themselves. UHS-I cards have a single row of pins on the back. UHS-II cards have two rows. In this example, both of these are SanDisk Extreme Pro cards, just different generations.

U1 vs U3 vs V30 vs V60 vs V90

The UHS-II code isn’t the only new code you’ll see on some microSD and SD cards. There’s also a new code that relates to suitability for recording high-resolution video. U1 and U3 have been around for a while; the new addition is V30.

All of these are speed classes aimed at recording high-resolution video. And they’re a separate designation from the UHS-I vs UHS-II one. I have more information on microSD speed classes here.

Memory Card Tools

Here are a few other related tools I’ve put together that can be useful when working with memory cards and data rates.

Converting Mbps to MB/s & X Speed Rating to MB/s

Another related and common calculation that often needs to be done when working with memory cards is converting the convention for measuring video bitrate (Mbps, Mb/s, or megabits per second) to the convention for measuring the speed of memory cards (MBps, MB/s, or megabytes per second).

So I’ve put together a simple calculator for that separately. You can find it here:

• Convert Megabits Per Second to Megabytes Per Second Calculator
• Convert Memory Card X Speed Rating to MB/s

Memory Card Size Calculators

If you’re trying to figure out what size memory card to buy, it can be useful to know how much video footage from the camera you can fit on a card. Here are a few tools that can be useful for that:

• Video Bitrate vs Memory Card Size Calculator
• How Much 4K Video Can 128GB Hold?
• How Much 4K Video Can 256GB Hold?
• How Much 4K Video Can 64GB Hold?

Working with Memory Cards

Here are some related posts for making sense of memory cards and working with them.

• Fastest SD Card Speed Tests. With cameras getting improved 4K, 5K, and even 8K video recording and burst shooting features all the time, some of them need the write speeds that only the fastest SD cards provide. So here’s a roundup of the fastest SD cards based on my independent tests.
• Fastest MicroSD Card Speed Tests. Need a fast microSD card? If you’re shooting 4K, 5K, or 8K video, high-speed burst-mode photos, or some other demanding use, speed matters. These are the results from my independent speed tests of the fastest microSD cards.
• Types of SD Cards Explained. There are several different types of SD cards, as well as multiple speed rating systems and cryptic codes. Here’s a rundown of what the differences are.
• UHS-I vs UHS-II on microSD & SD Cards. Wondering what the difference is between UHS-I and UHS-II with SD and microSD cards? Here’s an explanation.
• A1 vs A2 SD cards and microSD Cards You might have seen new A1 and A2 speed ratings on some of the newer SD and microSD cards. So what do they mean? And when should you take notice of it?
• SD Card Formatter App for Formatting, Wiping & Repairing SD & microSD Cards. Here’s a guide to using the SD Association’s official SD Card Formatter for preparing your SD and microSD cards for use.
• How to Format SD Cards on Mac. Here’s a step-by-step guide for formatting both SD and microSD cards.
• Best Free Data Recovery Software for SD Cards. Here’s a rundown of the best free data recovery software to use if you’ve accidentally deleted photos or videos from your SD card.
• How to Rover Deleted Photos from SD Card: SD Card Recovery Options. All those photos you took have disappeared from the SD card. The good news is that there’s still a good chance you can recover photos from the SD card. Here’s what to do. Includes free and paid SD card recovery options.

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