Read SD Card Ratings
V30, A2, U3, V90 — an SD card's label reads like alphabet soup, and buying the wrong rating means dropped 4K frames or a drone that refuses to record. This guide decodes every mark so you buy exactly the speed you need, nothing more.
TL;DR / Quick Fix
Quick fix: for SD cards, match the rating to the job — V30 handles 4K video, A2 means fast app performance, U3 is the speed class baseline for modern cameras. Buy from reputable brands; fakes lie about ratings. When in doubt, V30 A2 covers nearly every consumer need.
Follow these steps
- Learn the video speed classes. V10/V30/V60/V90 guarantee minimum sustained write speeds (10/30/60/90 MB/s). 4K video wants V30 minimum; 8K wants V60 or V90.
- Learn the UHS classes. U1/U3 mark minimum writes of 10/30 MB/s — the older system the V-ratings refined. U3 is the baseline for modern cameras and drones.
- Learn the A ratings. A1/A2 rate random read/write performance for running apps — phones and handheld consoles care. A2 is the faster tier.
- Match rating to the device. Action cam in 4K: V30 U3. Nintendo Switch: A2 for load times. Dashcam: high-endurance V30. The device manual usually names the rating — follow it.
- Buy real cards from real sellers. Counterfeit cards lie about ratings and capacity. Buy from reputable retailers, test with a speed benchmark on arrival, and beware deals too good to be true.
- Mind endurance for constant writing. Dashcams and security cameras murder regular cards — buy 'high endurance' rated ones. For SSD-style longevity questions, endurance ratings covers the bigger drives.
What NOT to do
- Do not buy the fastest card for a slow device. A V90 in a 1080p point-and-shoot wastes money — the device is the bottleneck.
- Do not trust marketplace no-name cards. Fakes dominate the cheapest listings — brand and seller both matter.
- Do not ignore the endurance rating for dashcams. Regular cards die in months of loop recording; high-endurance lasts years.
- Do not format in the wrong filesystem. exFAT for large cards in cameras; check the device manual — wrong formats cause 'card error' mysteries.
Frequently asked questions
What does V30 actually guarantee?
Minimum 30 MB/s sustained writes — enough for 4K video bitrates. It is a floor, not a ceiling.
Can I use any SD card in my Switch?
Yes, but A2-rated cards load games noticeably faster. Capacity matters more than extreme speed tiers.
Why did my 4K recording stop?
The card could not sustain the bitrate — classic under-rated card symptom. Step up to V30 or higher.