microSD & SD Memory Cards in Canada

A1 and A2 are Application Performance Class ratings guaranteeing minimum random read/write speeds for running apps directly from the card, common on Android devices and single-board computers. A1 guarantees at least 1,500 random reads and 500 random writes per second; A2 raises that to 4,000 reads and 2,000 writes, though the device itself must support A2 to benefit.

V30 is a Video Speed Class rating guaranteeing a minimum sustained write speed of 30 MB/s, the level most camera makers recommend for 4K video recording. Other common ratings include V10 (10 MB/s) and V60/V90 for higher-bitrate footage. Check your camera or drone's manual for its minimum recommended speed class before buying.

U1 and U3 are UHS Speed Class ratings. U1 guarantees a minimum sustained write speed of 10 MB/s, while U3 guarantees at least 30 MB/s, the same floor as V30. U3 cards are the better choice for full HD or 4K video recording and continuous burst photography.

The naming refers to capacity range and file system. microSDHC covers cards from 2GB up to 32GB, while microSDXC covers 32GB up to 2TB and uses the exFAT file system. Many older devices only support SDHC, so check your device's spec sheet before buying a card larger than 32GB to confirm SDXC support.

Your device only reads and writes as fast as its own card slot supports, so a UHS-I card in a UHS-I slot performs at its rated speed, while the same card in an older non-UHS device simply falls back to a slower speed rather than failing. Cards are backward compatible, so a faster-rated card than your device needs is safe, just without the extra speed benefit.