You just want to buy an SD (secure digital) card or microSD card for your DSLR, dash cam, drone, smartphone, or tablet. But one size doesn’t fit all. If the confusing array of memory card logos and specs has you pounding your head against a wall, we understand. We’ll give you the quick answers for most common memory card uses. (Pro tip: Check your device’s manual for memory card recommendations.)

If your needs are very particular, we’ve also delved deep into SD card standards to help you understand the difference between Class 10, V30, UHS-I, A1, and U3, so you can make the right choice for any device or purpose.

Secure digital (SD) card cheat sheet

Here are the short answers to which SD card to buy for which purpose:

  • Best SD card for video use: Concentrate on the Speed Class rating given for your device. Generally, a Class 10 card works for 4K video at 30fps. For anything higher, it’s recommended to invest in V30 and up. Go here for more details.
  • Best SD card for a GoPro Hero: For Hero 4 Black and older, a Class 10-rated card is generally fine but newer cameras such as the Hero 7 Black should be fed with U3 or V30-rated cards. Go here for details.
  • Best SD card for a DSLR: Choose a card based on its maximum write speed. While there’s no logo for that (thank god), 40MBps to 50MBps is typically good enough for most consumer and even some prosumer DSLRs. Go here for more details
  • Best SD card for an Android phone or tablet: Because of limitations in how these devices handle SD storage, storing apps on a card may frustrate you—though an A1-rated card may help a little. For storing photos or video, pay attention to the stated write speed. Go here for more details
  • Best SD card for a Nintendo Switch: For the best deal, skip the “official” card and buy a high-capacity card that works for your budget. Go here for more details.
  • Best SD card for a dash cam or nanny cam: Ignore the write speeds and X-ratings and go for one that touts “High Endurance.” Go here for more details.

SD speed class marks explained

One of the most confusing specs on SD and microSD cards is the dreaded “speed class” mark. For the most part, it’s pertinent only to recording video. Let’s say that again: It’s mostly intended for video.

Unlike with still photography or file storage, an occasional pause in data writes isn’t a big deal, as the camera or device should just pause and pick up where it left off. Video, however, requires undisturbed writes, because the stream can’t be easily paused on most consumer hardware.

The most familiar of these speed class designations is the basic numeric code of 2, 4, 6, and 10 that have been around since the mid-2000s. The number denotes the minimum write speed without a fatal (for video) disruption. A Class 4 card will write at 4MBps, for instance, and a Class 10 will write at 10MBps. 

10 SD Association

A Class 10 mark denotes minimum write speeds of 10MBps.

This was fairly straightforward until the U1 and U3 UHS Speed Class marks were introduced in 2010 and 2013, respectively. U1 and U3 indicate a respective minimum of 10MBps or 30MBps write speeds. Both also support a faster ultra-high-speed (UHS) bus.

toshiba class 10 v30 Amazon

Confused? This Toshiba microSD card carries speed markings for V30, U30, and Class 10.

To help muddy things even more, in 2016, a new Video Speed Class mark was introduced to increase speeds for even higher-resolution cameras and devices. Video Speed Class includes: V6, V10, V30, V60, and V90. As you can guess, the number denotes the guaranteed write speed in MBps (which in some cases can be lower than a card’s maximum write speed.)