How to Format an SD Card for the Steam Deck

Format the card inside the Steam Deck, not on your computer. On the Deck, go to Settings → Storage, insert the microSD card, select it, and choose Format — it takes a couple of taps and a few seconds, and from then on the card holds games. The reason you do it on the Deck is that SteamOS is Linux and formats the card with a Linux file system it can use natively, which a Windows PC cannot create for it. Do not format the card on Windows first; just put it in the Deck and let SteamOS handle it. Formatting erases everything on the card, so move off anything you want to keep before you start. It is one of the simplest jobs on the Deck, and the only thing to get right is doing it in the right place. The temptation to prepare the card on a PC first is exactly the mistake to avoid.

Why you format on the Deck, not the PC

A Steam Deck runs SteamOS, which is built on Linux, and Linux uses a different native file system than Windows does. When the Deck formats a card, it puts a Linux file system (ext4) on it, which SteamOS reads and writes efficiently. A Windows PC does not create that file system by default — it formats cards as exFAT or FAT32 — so a card you prepare on Windows is not in the Deck's preferred format, and the Deck will want to reformat it anyway. Skipping the PC step and formatting on the Deck is both simpler and correct. The SD Association defines the card standards, and Valve's Steam Support pages document the Deck's storage handling.

The steps

• 1. Insert the card with the Deck on. The microSD slot is on the bottom edge; push the card in (label side down, toward the back) until it clicks. SteamOS usually detects it immediately.
• 2. Open Settings → Storage. Press the Steam button, go to Settings, and choose the Storage section. You should see the microSD card listed alongside the internal drive.
• 3. Select the card and choose Format. Confirm the prompt. The Deck formats it with its Linux file system in a few seconds.
• 4. Set it as an install location if you like. Once formatted, you can install new games straight to the card, and move existing games onto it from the Storage screen without redownloading.

Formatting erases the card — back up first

This is the one warning that matters: formatting wipes everything on the card. If the card has photos, files or games from another device on it, copy those off to a computer before you format, because there is no undo. A brand-new card has nothing to lose, but a card you are repurposing does. Once it is formatted for the Deck, treat it as Deck storage — moving it back and forth between the Deck and a PC is not how it is meant to be used, since the PC will not read the Linux format normally.

Common mistakes and quirks

• Formatting on Windows first.Unnecessary and pointless — the Deck reformats it anyway. Go straight to the Deck.
• A card that will not show up. Reseat it firmly (it should click), make sure it is a microSD rather than a full-size SD in an adapter, and check it is not faulty by testing another card. A card that never appears may be a bad card or a seating issue rather than a format problem.
• Buying more card than the slot can use.The Deck's slot is UHS-I, so an ultra-fast card performs the same as a good value one in it — our Steam Deck storage explained guide covers why, and our best microSD cards for Steam Deck roundup picks the sensible ones.

That is the whole job. If you are weighing a card against a bigger internal drive, our SD card vs SSD upgrade guide compares them, and if you are still setting up a new Deck, our how to set up your Steam Deck guide covers the rest of the first-day steps.