You can use an external SSD to store PC games on either a Steam Deck or a ROG Ally, but the setup differs: the Deck runs SteamOS and offers a Linux desktop, while the Ally normally runs Windows. ASUS and Valve document microSD game storage more explicitly than external-SSD library setup, so use the instructions below to distinguish confirmed support from steps that depend on your launcher and current operating-system interface.
Before you start: what an external SSD changes
An external SSD connects by cable, usually to the handheld’s USB-C port or through an adapter or hub. The drive must stay connected whenever you want to access games installed on it. If you disconnect it while a game or launcher is using files on the drive, the game may stop working or the launcher may show the installation as unavailable. Close the game and launcher before disconnecting, and use the operating system’s safe-eject option when available.
A portable USB-C external SSD is the most direct product fit for this use. Check that the drive’s connector and included cable work with your device or adapter, and consider how you will charge the handheld while the drive is attached. Whether charging and storage can be connected at the same time depends on your particular port, adapter or hub arrangement; a hub with power delivery is optional, not universally required. No comparative speed or battery-life figures are established here.
Steam Deck: use SteamOS Desktop Mode, but don’t confuse SSD setup with microSD setup
What Valve documents
Valve says Steam Deck’s Desktop Mode works “like a normal PC”: users can browse the internet, download and install applications, and run programs outside Steam. That establishes a desktop environment, but Valve’s basic-use guide does not provide a complete official procedure for adding an external USB SSD as a persistent Steam game library.
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- Get NVMe solid state performance with up to 1050MB/s read and 1000MB/s write speeds in a portable, high-capacity drive(1) (Based on internal testing; performance may be lower depending on host device & other factors. 1MB=1,000,000 bytes.)
- Up to 3-meter drop protection and IP65 water and dust resistance mean this tough drive can take a beating(3) (Previously rated for 2-meter drop protection and IP55 rating. Now qualified for the higher, stated specs.)
- Use the handy carabiner loop to secure it to your belt loop or backpack for extra peace of mind.
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Valve does document a route for formatting a microSD card: Steam > Settings > System > Format SD Card. That instruction applies to the Deck’s microSD card, not an external SSD. Do not assume an external drive uses the same format, mounting behavior or library-persistence process.
Installing and launching from an external SSD
- Connect the drive. Attach the SSD to the Deck and enter Desktop Mode using the Deck’s power menu. Valve’s guide describes Desktop Mode as the place to browse, install applications and run programs outside Steam.
- Use the current Steam interface to choose storage only if the drive is available there. The official support material cited here does not establish the exact steps for formatting or adding an external drive as a Steam library. Do not proceed by applying the microSD instructions to the SSD, or by assuming a particular filesystem or mount point.
- Choose the SSD as the install location in Steam only after Steam recognizes it as a library location. If it is not offered, consult current SteamOS/Steam support or a device-specific, current community guide rather than guessing at drive settings.
- Keep the SSD connected to play. Start the game from Steam as usual. If the library or game is unavailable after reconnecting or restarting, confirm the drive is connected and recognized before attempting to reinstall.
Valve’s Steam Deck basic-use guide covers Desktop Mode and the microSD formatting route. Its SteamOS page and SteamOS installation and repair guide provide broader operating-system support, but are not an external-SSD game-library walkthrough.
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- Capacity Display Variance: 500GB external ssd often appears as around 465GB on Windows. MacOS can show full 500 GB capacity. This is binary calculation difference and doesn’t affect SSD hard drive actual physical storage
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ROG Ally: install through Windows launchers and manage the library in Armoury Crate SE
Install a game to the external SSD
The Ally normally uses Windows, so install-location choices are made in the game launcher or Windows workflow, rather than by treating Armoury Crate SE as the installer. ASUS says the Ally supports major PC launchers, including Steam, Xbox Game Pass, Epic Games Launcher, Ubisoft Connect, EA App and GOG Galaxy; downloaded games are automatically imported into Armoury Crate SE’s Game Library.
- Connect the SSD to the Ally. If you need to charge while it is connected, use a compatible arrangement that supports both; whether an adapter or hub is needed depends on your hardware.
- Open the launcher for the game. When installing, select the external SSD as the destination using that launcher’s install-location control. The exact label and sequence vary by launcher and version, so follow the current interface rather than relying on one universal Windows path.
- Let the installation finish, then open the game from its launcher or Armoury Crate SE. Armoury Crate SE is a library interface: ASUS says installed games are added automatically. If a game is missing from the library, use Manage Library > Add Game/App to Library.
- Leave the drive connected while playing. Close the game and launcher before disconnecting it. If a title later appears unavailable, reconnect the SSD and check its launcher installation before starting a new download.
Armoury Crate SE does not uninstall the game
Removing a game tile from Armoury Crate SE removes the library entry, not the installed game. ASUS directs users to uninstall through the game’s launcher or Windows’ Add or Remove Programs settings. This distinction matters when troubleshooting a game that disappears from the library after moving or disconnecting its storage.
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ASUS explicitly documents installing games to the Ally’s microSD storage, but the cited FAQ does not make the same explicit statement for external USB SSD game installs. Its launcher and library guidance supports the Windows workflow above; it is not a device-specific guarantee about external-drive formatting or how every launcher handles a disconnected library.
See ASUS’s ROG Ally Series Frequently Asked Questions for its current launcher, microSD and Armoury Crate SE guidance. The page was last updated June 3, 2026.
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External SSD or microSD?
| Consideration | External SSD | microSD |
|---|---|---|
| Connection | Cable-connected over USB; the drive must remain attached to access its games. | Onboard card seated in the device. |
| Documented game-storage guidance | The cited manufacturer support pages do not provide a complete official external-SSD library setup for either handheld. | ASUS says Ally games can be installed to microSD. Steam documents the Deck microSD formatting route in Steam > Settings > System > Format SD card. |
| Library handling | Use the relevant Steam or Windows launcher once it recognizes the game location; exact behavior can depend on platform and launcher. | Still managed through the relevant platform or launcher; the card’s presence does not replace that library management. |
| Charging while using storage | Depends on the handheld, port and adapter or hub arrangement; a USB-C hub with power delivery may help where simultaneous connection is needed. | Does not occupy the USB port, leaving that connection available for charging. |
Choose an external SSD if removable, cable-connected storage suits how you use the handheld and you can keep it attached during play. Choose microSD for onboard convenience; it has clearer manufacturer-documented game-storage guidance in the sources cited here. Neither option has a speed or battery advantage established by the available evidence.
Quick Recap
Best Value
- NEARLY 2X FASTER THAN OUR PREVIOUS GENERATION(8) – move 1,000 high-res photos in under 60 seconds(6) with up to 2000MB/s transfer speeds(2).
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- 256-BIT AES ENCRYPTION(4) – helps keep private files secure with password protection.
When a game is unavailable after disconnecting the drive
- Reconnect the SSD before opening the game. A title installed on removable storage cannot be accessed while that storage is disconnected.
- Check the launcher’s library or install status. On the Ally, Armoury Crate SE can show a library entry, but it is not the installer or uninstaller of record.
- Do not remove a library tile as a substitute for uninstalling. On the Ally, ASUS says removing the tile does not uninstall the game; use its launcher or Windows Add or Remove Programs instead.
- Do not format or move files based on the Deck’s microSD instructions. Those instructions are specifically for microSD, and the cited Valve guidance does not establish external-SSD filesystem or remount behavior.
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