How to read A2 and V30 on a microSD card

Photograph: Raspberry Pi Ltd, SD Cards documentation, CC BY-SA 4.0. Original JPEG unchanged. A Raspberry Pi microSD card in a Raspberry Pi 5, shown in the manufacturer’s documentation. Documentation · Exact original source · Licence.

A microSD card can carry A2, V30 and a large capacity number on the same tiny face. Those marks describe different things. If you are buying a card to run a small computer, check the device’s support for application performance. If you are buying it to record video, start with the camera’s required write class and supported card list.

Evergreen buying guide, checked 11 November 2026. Write down the exact device and its most demanding job. For a Raspberry Pi boot drive, look up the board’s application-class support; for a camera spare, look up the camera’s recording requirements.

For apps and boot drives, check A1 or A2 and the host

Opening an application or running an operating system can involve many small reads and writes in different places. Application Performance Class covers those operations as well as a sequential write floor. A2 specifies higher minimum random performance than A1 under the standard’s conditions. It uses features including command queueing and a cache; the SD Association says A2 performance requires support from both the card and the host. Use your board’s documentation to see which card features it supports. Application Performance Class.

Raspberry Pi gives a useful example. Its documentation lists 4 kB random reads and writes for its own SD cards on two boards: 3,200 and 1,200 operations per second on Pi 4 using DDR50, versus 5,000 and 2,000 on Pi 5 using SDR104. The figures describe the supplier’s 4 kB random tests on those specific combinations. Raspberry Pi’s 2024 launch note also explains the software support needed to use command queueing on Pi 5. Card documentation · Launch and host support.

For recording, check the sustained write class

A camera needs to keep writing a stream as it records. V30 denotes a 30 MB/s minimum sequential write class under the standard’s conditions, with a compatible host and mode. The large “up to” read figure on the packaging describes peak read speed. Check the write class separately. Use the camera maker’s guidance for the recording mode you actually need, and match the indicated class and interface. SD Speed Class · What the V numbers mean.

The DJI Osmo Action 5 Pro list illustrates the difference. It includes a 32 GB SanDisk Extreme PRO marked A1 and V30, and a 64 GB Kingston Canvas Go! Plus marked A2 and V30. They are both on that specific camera’s list, despite the different application classes. Use that list for the Osmo Action 5 Pro. For a different camera, look up that model’s own list. DJI’s recommended models.

What to ask for at the shop

• Record the full device model and the exact job: booting and running apps, or capturing a stated video mode.
• Look up the device’s supported capacity family and size limit, then pick the size you need.
• For a Pi or other small computer, check which application class and card features the board and installed software support. For recording, check the maker’s recommended card or matching write class.
• Match the exact card model and capacity, then confirm seller returns. Keep your existing card and files until the replacement works for the job.

Take that note to a local retailer in London, Lagos or Nairobi, or use it to compare online listings. If a listing gives only a brand and a headline speed, ask for a photograph of the packaging or the full model number. Check stock and support terms with the seller in your country. Capacity and compatibility.

See also: how to check what a USB-C cable can do.