The Steam Machine's front microSD slot is the easiest way to add game storage without ever opening the console — and because SteamOS shares card libraries, a card you fill on a Steam Deck drops straight into the Machine and its games show up right away. All three picks here are proven UHS-I cards sized for a real game library: the SanDisk Extreme is our best overall, the Samsung PRO Plus is the best value, and the Lexar Play 1TB is the pick when you just want the most room.
One thing decides almost everything about this choice, and it's easy to get wrong: the Steam Machine's card reader is UHS-I, the same class as the Steam Deck's. In the real world that tops out around 100 MB/s no matter what the card is rated for. So the expensive new microSD Express cards (rated 800–900 MB/s) are wasted money here — the slot can't use that speed, and they fall back to UHS-I. Buy a good UHS-I card instead and spend the difference on capacity. For the fastest loads and your main library, the internal drive is the real upgrade — see our best SSDs for the Steam Machine guide; a microSD card is the cheap, no-tools way to add overflow space on top.
Who this comparison is for#
- Anyone who bought the Steam Machine and wants more room for installs without opening the case or touching the internal drive.
- Steam Deck owners who want one card that carries their library between the Deck and the Machine.
- People who'd rather spend on capacity than on peak speed the UHS-I slot can't actually deliver.
How we picked#
- UHS-I, not Express. The slot is UHS-I, so every pick is a top UHS-I card. We deliberately skipped microSD Express cards — the reader can't use their speed, so they're a waste here.
- A2 for load times. With sequential speed capped by the slot, the rating that still matters is A2 (random read/write). A2 cards handle a game's many small file reads better, so levels and menus load quicker. All three are A2, U3, V30.
- Capacity that fits a modern library. Games are large, so we weighted usable space heavily and picked cards that scale to 512GB and 1TB.
- Proven in handhelds. Every card here has a long track record in the Steam Deck and Switch — known controllers, real endurance, no anonymous cards. And to be clear about what a card does: it stores and runs games, but it will never load or run a game as fast as the internal M.2 drive. It's the convenience-and-capacity option, not the speed option.
Product 1 — SanDisk Extreme microSDXC (Best Overall)#
The SanDisk Extreme is the card most Steam Deck owners already trust, and that track record is exactly why it's the safe pick for the Machine. It's A2-rated with strong random performance, so games with lots of small assets load about as fast as a UHS-I slot allows, and its sustained write speed comfortably handles dropping a big game onto the card. You're buying a known quantity: mature controller, consistent real-world results, and a long history in exactly this kind of handheld-console use.
It's also built for a device that travels between rooms and bags — it's shockproof, temperature-proof, waterproof and X-ray-proof, and it ships with SanDisk's RescuePro file-recovery software. At 512GB it holds a serious stack of installs, and the same card slots straight into a Steam Deck, so your library follows you. This is the card to buy if you don't want to think about it.
Key specs#
Interface : microSDXC, UHS-I (U3)
Speed class : A2, U3, V30, Class 10
Rated read : Up to ~190 MB/s (slot-limited to UHS-I in the Machine)
Durability : Shock, temperature, water and X-ray proof
Capacities : 256GB / 512GB / 1TB
Warranty : Limited lifetime
Best for : Anyone who wants the proven, no-second-guessing card
Bottom line. The default handheld card for a reason — strong A2 random speed, tough build, and a long track record. The safe best-overall choice for the Machine.
Product 2 — Samsung PRO Plus microSDXC (Best Value)#
The Samsung PRO Plus is the card to buy when you want almost everything the Extreme offers for less. It's A2, U3 and V30, matches the important random-read behavior that drives load times, and Samsung's cards are known for running cool and staying reliable over years of use — a nice quality in a card that lives in a console and gets written to a lot. For the money, it's hard to beat as an everyday Steam Machine card.
Samsung backs it with the same six-proof protection (water, temperature, X-ray, magnet, drop and wear-out) and a long warranty, so it's every bit as travel-safe as the Extreme. At 512GB it's the sweet spot: enough space for a real rotation of games without paying the 1TB premium. If you want the best balance of price, durability and speed, this is the one.
Key specs#
Interface : microSDXC, UHS-I (U3)
Speed class : A2, U3, V30, Class 10
Rated read : Up to 180 MB/s (slot-limited to UHS-I in the Machine)
Durability : Six-proof; 10-year limited warranty
Capacities : 128GB / 256GB / 512GB
Best for : The best all-round value for most players
Bottom line. Nearly all of the Extreme's strengths — cool, durable, A2-fast — at a friendlier price. The smart value pick.
Product 3 — Lexar Play 1TB microSDXC (Best Big Capacity)#
If your problem is simply "not enough room," the Lexar Play 1TB solves it. It was built for exactly this job — expanding storage on handheld consoles — and 1TB is enough to keep a large library installed and ready without constantly uninstalling to make space. It's A2, U3 and V30, so it behaves like the others in day-to-day loading; the difference you're paying for is capacity, not speed.
Because the slot is UHS-I, the Play loads games at the same real-world pace as the smaller cards here — buying 1TB is about never running out of space, not going faster. That's the honest trade: you pay more per game stored, but you stop managing installs. If you have a big backlog and want it all on the Machine (and portable to a Deck), this is the card.
Key specs#
Interface : microSDXC, UHS-I (U3)
Speed class : A2, U3, V30, Class 10
Rated read : Up to 160 MB/s (slot-limited to UHS-I in the Machine)
Marketed for : Handheld consoles and gaming devices
Capacities : 256GB / 512GB / 1TB
Best for : Keeping a large library installed at all times
Bottom line. The most space here, purpose-built for handheld gaming. Buy it for the 1TB, knowing the speed matches the cheaper cards.
Which one should you buy?#
For most people, buy the SanDisk Extreme 512GB. It's the proven handheld default — strong A2 random speed, tough build, and years of reliable use in exactly this role. It's the card you never think about again.
If you want the same everyday experience for less, buy the Samsung PRO Plus 512GB. It matches the Extreme where it counts, runs cool, and is usually the better deal — the best value for a Steam Machine.
If you're out of space and want to stay that way, buy the Lexar Play 1TB. Just go in knowing you're paying for capacity, not speed — every card here loads at the same UHS-I pace.
Whichever you pick, skip microSD Express cards — the slot can't use their speed. And remember a card is the easy overflow option: for your main library and the fastest loads, the internal drive is the real upgrade in our best SSDs for the Steam Machine guide, and the rest of the setup is in our best Steam Machine accessories roundup.
FAQ#
Does the Steam Machine support fast microSD Express cards?#
No — its card reader is UHS-I, the same class as the Steam Deck. A microSD Express card will physically work but drops to UHS-I speed, so you'd be paying for performance the slot can't use. A good UHS-I card (like the three here) is the right buy; put the money you save toward more capacity.
Will a microSD card load games as fast as the internal SSD?#
No. The internal M.2 drive is far faster and is the right place for your main library and the games you want loading quickest. A microSD card is the cheap, no-tools way to add overflow space — great for a large backlog, not for the fastest loads. See our best SSDs for the Steam Machine guide for the internal upgrade.
Can I move a card between my Steam Deck and the Steam Machine?#
Yes. SteamOS shares card libraries, so a microSD card you've set up on a Steam Deck drops into the Steam Machine and its installed games show up immediately — and the same works in reverse. One card can carry your library between both.
What size microSD card should I get?#
512GB is the sweet spot for most players — enough for a solid rotation of modern games without overpaying. Go 1TB (the Lexar Play) if you keep a large library installed and don't want to manage space. Below 256GB fills up fast with today's game sizes.
What do A2, U3 and V30 mean, and which matters here?#
They're speed ratings. U3 and V30 guarantee sustained write speed for installing large games. A2 is about random reads and writes — the small-file access that affects how quickly levels and menus load. Because the slot caps sequential speed, A2 is the rating that still makes a real difference, and all three picks are A2.