Tutorials · PC

Steam Deck: format a microSD card in SteamOS

1 November 2026

Adding a microSD card to keep more games on your Steam Deck? Prepare it in SteamOS after backing up its contents, then check that it appears in storage settings. This guide covers Steam Deck LCD and OLED.

Explanatory illustration: Steam Deck: format a microSD card in SteamOS — Explanatory illustration — simplified representation; follow the written steps.

Before you start

Steam Deck LCD or OLED running SteamOS in Gaming Mode. This is not a Windows-on-Deck procedure. You need a compatible microSD card and, if it contains files, another device with a suitable reader and enough space for a backup. Keep enough battery charge or connect power.

1. Check what is already on the card

Formatting erases the microSD card. If you have used it in a phone, another console or a computer, copy the files you want to keep to another device first. Open a few copied files to confirm they can be read before continuing.

Do not format a card as a repair attempt when your actual goal is to recover its data. Stop here if you do not know what it contains. Preparing new storage and recovering existing files are different tasks.

2. Insert the microSD card

Locate the microSD slot along the bottom edge of the Steam Deck and insert the card without forcing it. Return to SteamOS Gaming Mode: this procedure uses the console’s settings, without opening its case or using PC partitioning software.

Valve’s hardware guide covers LCD and OLED models and specifies a UHS-I microSD card rated U3 or better. UHS-II and UHS-III cards can work, but the reader does not benefit from their additional speed. Check the exact card specification if you are uncertain.

3. Start formatting in SteamOS

Press STEAM and open Settings.
Select System and find Format SD card.
Read the confirmation. If useful files remain on the card, cancel and back them up first.
Let the operation finish without removing the card or interrupting power. Valve notes that it may take a few minutes.

A temporarily busy button does not, by itself, prove that the card is faulty. Wait for the operation’s result and use any actual error message to guide troubleshooting.

4. Verify the available storage

Open STEAM → Settings → Storage. Check that the microSD card appears among the storage devices and shows available space. This is the checkpoint before installing or moving games.

Expected result: after formatting finishes, the card is recognised in storage settings. If it is absent, do not treat preparation as complete.

Valve’s FAQ states that Steam Deck formats microSD cards as ext4 with casefolding. You do not need to choose this in an external utility to follow this guide. Do not reformat the card in Windows merely because its contents do not appear like those of an ordinary USB drive.

If the card cannot be formatted

An error appears: record its exact wording, the card model and capacity. Avoid repeated formatting attempts without identifying what failed.
SteamOS is out of date: Valve recommends available updates and a restart as initial troubleshooting steps. Then check storage again.
Important files remain: stop destructive attempts and prioritise recovery from another device.
The card remains missing or the error returns: contact Steam Deck support with the message and the checks already performed. Lack of detection alone does not prove a failed reader.

If the card is recognised but an installed game behaves incorrectly, diagnose that separately. Verifying a Steam game’s files concerns its installed content; it is not the same operation as formatting the storage device.

Sources and scope

Translated from the French guide based on official documentation checked on 2026-10-15. This guide does not claim physical testing on your equipment. LODEX’s preparation and result checks are practical advice; follow any warnings shown by your device.