How to install and format an SD card on Steam Deck – Polygon

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What speeds and formats work with the Steam Deck
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Depending on what model you get, your Steam Deck could come with 64, 256, or 512GB of onboard storage. With the size of today’s games, though, that’s not going to get you far — Call of Duty: Warzone 2.0 runs about 125 GB and the forthcoming Forspoken wants a whopping 150GB.
Luckily, the Steam Deck comes with a slot for a microSD card to expand your storage options. Our Steam Deck microSD card guide will walk you through how you can format an SD card and how you can pick out a size, alongside an explanation of various speed classifications.
Quite simply, a microSD card expands the storage of your Steam Deck as another place to store your downloaded games. With a bit of work, you could store your screenshots on it as well if you really wanted to.
The Steam Deck wants a microSD card in the ext4 format — a Linux format, which makes sense, since SteamOS runs on Linux.
The fastest way to get it formatted for you Steam Deck is to use the Steam Deck itself to format the card. Plug the microSD card into the slot on the bottom of the Deck — it’s on the bottom below the lower right corner of the screen. The card goes in face up. You might have to use a fingernail to get it to click into place.
Hit the Steam button, go to Settings > System and then scroll down to System Settings. Under Format SD Card, hit Format. Formatting will erase the card and you’ll get a warning saying as much. After a few minutes, your card will be good to go.
To set microSD card as the default storage, go to Settings again and scroll down to Storage. At the top, you’ll see your Internal Drive and the new MicroSD Card. If this is the first time you’ve used an SD card, you’ll have to move over to highlight the Internal Storage and hit X to Make Default and set the default storage. Then you can move over to MicroSD Card and Make Default on that one.
Regardless of whether or not you’ve set it as default, the next time you Install a game, you’ll get the option of saving it to the Internal Drive or the MicroSD Card.
The short answer here is: the biggest storage size you want to spend the money on. As you’d expect, bigger storage sizes cost more.
They’ll vary a little in their data transfer (and read and write) speeds — we’ll talk more about that below, if you’re really interested.
As the price of microSD cards continues to drop, you’ll have a lot of options here with everything from two 32GB cards for under $10 all the way up to a 1TB card for about $175. The main criteria here are what you want to spend and how big the games you want to store are.
As some quick examples from Amazon, here is a selection of the microSD cards you can find:
The Steam Deck supports SD, SDXC and SDHC microSD cards. Those letters after SD represent the storage size — a regular old microSD card stores up to 2GB, microSDHC (High Capacity) cards hold up to 32GB, and microSDXC (Extended Capacity) cards hold over 64GB. Even if the listing doesn’t say XC or HD, it’ll probably be stamped on the card itself as a logo. And, realistically, if you’re looking to meaningfully expand your Steam Deck’s storage, it’ll be an XC.
Any microSD card you find is going to have some combination of a bunch of other gibberish numbers and letters stamped on it as well. There are Roman numerals, As, Cs, Us, or Vs next to various numbers. These all indicate the speed standards that card follows. The standards involve words like “bus” and “non-fragmented” and “sequential.” They’re all generally about data speeds, though, and bigger numbers are better.
Nothing about the classifications are mutually exclusive — they’re just different ways of measuring data speed. Generally speaking, the microSD cards for Steam Decks that you’re looking for will have classifications like either A1 or A2 (A2 is better), C10, or U1 or U3 (U3 is better), and those are all (super roughly) equivalent for your purposes.
Cards with a V number (the V is for video) will have the (roughly) highest speeds — that standard is for reading and writing 4K video — but they’re also going to be the most expensive. V30 seems to be the most readily available, but you may also find V60 or V90.
If you’re lucky, it might also simply list the speed (or indicate it in the listing). That’s, you know, the speed — probably between 100 and 160MB per second. Yes, faster is better, but you’re probably not going to notice much difference.
The Roman numeral is the only one that is limited on a Steam Deck. The Roman numeral — I, II, or III — indicates the card’s Ultra High Speed (UHS) spec. This is another speed-related classification, but UHS-II and -III also have a different physical layout with a second row of pins on the back. UHS-II and -III are backward-compatible, but that means you’ll be limited by the speed of what you plug it into. All of which is to say that anything over UHS-I will be limited by the Steam Deck itself which maxes out at 170MB/s (or, occasionally, 180MB/s).
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