UHS-I vs UHS-II: What’s the Difference?

The difference between UHS-I and UHS-II SD cards is in their design and speed. UHS-II cards have an extra set of connectors, making for much faster transfer speeds than the older UHS-I designs.

My name is Caleb, and I’ve done plenty of work with SD cards over the years as a photographer. In this article, I’ll explain the difference between UHS-I and UHS-II SD cards, whether the latter is worth paying more for, and which devices each one is compatible with.

If you’ve seen both of these terms thrown around and are unsure which one suits your needs, keep reading for a complete explanation.

The Difference Between UHS-I and UHS-II

The max transfer speed, which measures the amount of data the card can read or write continuously, is the difference between UHS-I and UHS-II cards. The former can transfer data at up to 104 MB per second, while the latter has a faster maximum speed of 312 MB per second.

The faster transfer speed is made possible by the UHS-II’s improved design, which includes an extra row of connectors that interface with the device.

Why does this design change matter? If you’re performing a task that requires writing a lot of data at once, like recording 4K footage or taking photos in bursts, you need an SD card that can keep up with the massive amount of data.

Because of the increased speed, you can also expect to pay more for a UHS-II SD card. If you often need to move files from your SD card to a device, this upgrade in speed might make the cost increase worth it.

UHS-I and UHS-II Compatibility

You can use UHS-II cards in devices meant for their UHS-I counterparts. Similarly, the older UHS-I cards will still work in newer UHS-II devices.

That said, using a UHS-II card in a UHS-I device will limit the max transfer speed to the UHS-I’s 104MB per second since the device can’t take advantage of the UHS-II’s extra connectors.

So, if you only have devices rated to accept UHS-I SD cards, using a UHS-II card won’t provide any benefits.

Difference Between UHS Class and Write Speed

You might have noticed that the UHS class of the card is listed separately from the read and write speeds. 

That’s because the UHS class, such as UHS-I or UHS-II, only represents the maximum transfer speed that the card can physically handle. The card’s actual transfer speed might not actually reach that limit.

So, before buying a card, make sure you check both the UHS class and the write speed of the specific model. For example, while a UHS-I card can handle data transfers of up to 104MB/s, the actual write speed of a certain SD card might only reach 90MB/s.

Do I Need a UHS-II SD Card?

The answer depends on how you use your SD cards. For everyday use, UHS-I SD cards will usually do just fine. UHS-II SD cards are meant for more intensive use and are more fit for enthusiasts or professionals.

Also, before getting a UHS-II card, ensure your device is compatible. Otherwise, you’ll spend extra for no actual performance increase.


Here are some frequently asked questions about UHS-I and UHS-II SD cards.

Is UHS-II Better Than UHS-I?

Yes. UHS-II cards perform better in a key area, write speed, because they have an extra set of connectors.

Do I Need UHS-II For 4K Video?

UHS-II is the better option for 4K videos, as the excellent max transfer speed will let you write plenty of data at once without dropping frames or running into other performance issues.

Why Are UHS-II Cards Expensive?

UHS-II SD cards cost more because of their performance increases in transfer speed.


UHS-II SD cards have extra connectors, giving them a faster possible write speed than UHS-I cards when used with compatible devices. This makes them more expensive, but also useful if you need to move large files.

Do you use UHS-I or UHS-II SD cards? Let us know in the comments!

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