The microSD is the heart of an Atmosphère patch: it holds Atmosphère, hekate, and, if you choose, a copy of the Switch's internal memory (emuMMC). A failed format is the leading cause of a console refusing to boot.
exFAT or FAT32 Format?
FAT32 is the safe choice. The Switch's exFAT implementation is known to be fragile and regularly corrupts cards. FAT32 requires splitting files larger than 4 GB, which the tools handle automatically.
A Real Card, Not a Fake
Buy a brand-name card from a reputable retailer and verify its actual capacity with a testing tool before putting anything on it.
Back Up First
Formatting erases everything. Copy the current contents of your card to your computer before you begin.
Space Calculator
Enter your card size and what you plan to put on it: the calculator will tell you if there's space left, and how much.
Helpful reminder: an advertised 128 GB card provides about 119 GB of actual usable space (manufacturers count in billions of bytes). The calculation above accounts for this and maintains a small safety margin.
How long does it take?
An estimate of the installation time (card preparation, file copying, emuMMC, backup) and the duration of the first boot, depending on your console model and card speed.
These durations are estimates measured under normal conditions: a slow card, a USB 2.0 reader, or an unexpected issue can easily double the total time. Plan for extra time and never rush your work.
Step-by-step Guide
Check if your console is compatible.
Without a boot exploit, preparing the card is useless. First, use the serial number checker.
Back up the card's current contents.
Copy everything to your computer, including the Nintendo folder which contains your official games and save data.
Format as FAT32, single partition.
On Windows, the built-in tool refuses to format cards over 32 GB as FAT32: use a partitioning utility. On macOS, Disk Utility offers "MS-DOS (FAT)". Allocation unit size: 32 KB works well.
Prepare an emuMMC partition if you want a dedicated one.
hekate can do this itself (Tools → Partition SD Card) and resize the card without needing a PC. This is the most reliable method.
Copy Atmosphère to the root.
Unzip the official archive: you will get atmosphere/ and hbmenu.nro at the root of the card. Check that your Atmosphère version supports the firmware installed on your console.
Copy hekate and its configuration.
The hekate_ipl.ini file goes into bootloader/, along with the payload.bin payload expected by injectors. Add a theme/nyx if you want, it's not required.
Add useful extra files.
File manager, internal memory backup tool, save manager: each application goes into the switch/ folder.
Safely eject the card,
insert it into the powered-off console, put the console in RCM mode with a jig, then send the hekate payload from your PC or phone.
Create the emuMMC from hekate
(emuMMC → Create emuMMC), then launch Atmosphère on this emuMMC. The original internal memory remains untouched.
Immediately back up the internal memory
(Tools → Backup eMMC: BOOT0/BOOT1 and the keys). Store this backup off the card: without it, an error could be unrecoverable.
Common Errors
Card is exFAT. It works at first, then the card gets corrupted and games disappear. Reformat to FAT32.
Nested folders.atmosphere/ and bootloader/ must be at the root, not inside a subfolder from the unzipped archive.
Outdated Atmosphère version. Each version only supports a specific range of firmwares: updating the system without updating Atmosphère will prevent it from booting.
Hot-swapping the card. Always power off the console before removing the card, otherwise the filesystem will break.
Using one card for two consoles. Identifiers and the emuMMC are unique to one console: mixing them is a sure way to get banned.
Counterfeit card. A card sold as 512 GB that only holds 32 GB will cause immediate corruption; test the real capacity beforehand.
This information is provided for educational purposes, for hardware that you own. Modifying a console voids the warranty and can lead to a permanent ban from online services — see the Basics page.