What is Speed Class?
The speed class of an SD (Secure Digital) card refers to its minimum sustained write speed.
There are currently four main speed classes for SD cards: Class 2, Class 4, Class 6, and Class 10. Class 2 SD cards have a minimum sustained write speed of 2 MB/s, while Class 4 cards have a minimum sustained write speed of 4 MB/s. Class 6 SD cards have a minimum sustained write speed of 6 MB/s, and Class 10 cards have a minimum sustained write speed of 10 MB/s. In addition to these main speed classes, there are also two Ultra High Speed (UHS) speed classes: UHS Speed Class 1 (U1) and UHS Speed Class 3 (U3). UHS-I U1 cards have a minimum sustained write speed of 10 MB/s, while UHS-I U3 cards have a minimum sustained write speed of 30 MB/s. The speed class of an SD card is important to consider when using it for tasks that require fast write speeds, such as recording high-resolution video. Using a card with a lower speed class may result in dropped frames or other issues during recording.