microSD Express

It looks like any other microSD card. Inside, it talks to the console the way an SSD does, and the console knows the difference.

The short answer

microSD Express is a microSD card that adds a PCIe and NVMe interface next to the classic SD interface [2][3]. Under SD Express, the SD Association (SDA) lists 985 MB/s for PCIe Gen3 x1 and 1970 MB/s for PCIe Gen4 x1, against 104 MB/s for UHS-I (SDR104) [1]. These are bus speeds, an upper limit of the interface, and the SDA states that the maximum speed of a card differs from the speed of its bus interface [1]. The card matters most for the Nintendo Switch 2, where expansion storage must be a microSD Express card [5]. Our assessment: buy it only if a device asks for it, and treat a card in an older device as an ordinary microSD card.

How it works

1. Two interfaces on one card. SD Express puts PCIe and NVMe into SD cards alongside the legacy SD interface. SDA introduced it with the SD 7.0 specification [3]. The idea is that the card can behave like a removable SSD [3].
2. More pins. A microSD card has 8 pins for UHS-I, 16 for UHS-II, and 16 to 17 for a one-lane SD Express card. The first row of pins stays compatible with the older cards [2].
3. Backward compatible. SDA says SD Express keeps the long-standing backward compatibility of SD, because the PCIe interface is added alongside the existing UHS-I interface [3]. In a device that does not know SD Express, the card works at normal microSD speed. Nintendo says the same for its first console: an Express card in a Nintendo Switch runs at microSD speed [5].
4. Speed tiers. microSD Express with PCIe Gen3 x1 comes in at 985 MB/s in SD 7.1 (SD 7.0 defined SD Express for full-size cards only). With PCIe Gen4 x1 the SDA lists 1970 MB/s [1]. The SD 9.10 press release says microSD Express was introduced in SD 7.1 with NVMe at 985 MB/s, and the Addendum Version 8 doubles the maximum [4]. Our reading: the Gen4 cards are the newer generation, so check which one your device supports.
5. Bus speed is not card speed. A card rated for a high bus speed can still write slower than the interface allows, and the SDA says so on its own speed page [1].
6. A case where it is required. Nintendo states that the Switch 2 only works with microSD Express cards for additional storage, up to 2 TB (state at retrieval) [5]. The console has 256 GB of internal storage, and the expansion slot accepts microSD Express cards up to 2 TB [6]. Our reading: the console works without a card, and the card extends storage.
7. Old cards do not carry over. According to Nintendo, a microSD card previously used with a Nintendo Switch cannot save or load digital games or save data on the Switch 2, and the first use needs a system update [5].

A practical example

You want more room for downloaded games on a Switch 2. You check the card packaging for the words microSD Express, check the size against the console's limit of 2 TB, and install the system update before you insert the card [5][6]. You also keep your old Switch microSD card for the first console, because it still works there [5]. We have not documented a console or a card in our inventory (14 to 16 Oct 2026), so this is a generic walk-through.

Checklist

• Check the device manual or the maker's support page for "microSD Express" before you buy [5].
• Match the card's PCIe generation and capacity to what the device supports [1][6].
• Do not read the bus speed on the package as the speed you will get [1].
• Update the console before first use, and keep in mind that save data stays in the console's system memory and never moves to the card [5][7].
• Keep old microSD cards for devices that do not know Express [3][5].
• Look at the pin side if you are unsure: Express cards have a second row of contacts [2].