Your SD card’s file system might be stopping you from transferring large files, but there’s an easy fix for that.
SD card capacities have grown by leaps and bounds since hitting the market in the early 2000s, and the best microSD cards now come in capacities from 128GB up to a massive 1TB. No matter how capacious your SD card, though, you may run into an unexpected limitation: it won’t accept files larger than 4GB, even when there’s enough space left.
While it may seem worrying, the good news is that the SD card itself is almost certainly fine. Instead, the problem lies in the file format it’s currently using. More specifically, it’s FAT32, a file system that dates back to Windows 95 and is still commonly used today. Although it’s widely compatible and can be read by almost any device, it has a major downside: no single file can be larger than 4GB.
FAT32’s 4GB-per-file limit comes down to how it records file sizes using a 32-bit number. In computing, the largest value that fits within this limit is 4,294,967,295 bytes, or nearly 4GB. The SD card can physically hold files over 4GB, but the file system prevents it. That’s usually fine if you only store documents and photos, but it can quickly become a problem if you want to store 4K videos, for example. In that case, you’ll need to reformat your microSD card to exFAT, another file system designed to overcome FAT32’s limitations — including support for files larger than 4GB.
How to format your SD card on Windows and macOS
First, back up all the files on your SD card, since this process will erase everything. Also, if you’re using very old tech (like a camera that’s more than a decade old), it may not support exFAT. Microsoft added exFAT support in Windows Vista SP1, while Apple added it with OS X Snow Leopard. If your device predates either OS, it’s probably best to keep your SD card formatted as FAT32.
On Windows, open File Explorer to format your SD card. Click This PC, then right-click on your SD card. Select Format from the menu that appears and choose exFAT under File System. Here, you can also choose whether to run a Quick Format or rename the volume. The process is the same as formatting a microSD card or a USB drive. On a Mac, use the Disk Utility app instead (you can quickly find it using Spotlight). With the app open, go to the View menu and click Show All Devices. Select your SD card — not the volume listed under it — then click Erase. Set the format to exFAT, name the volume and confirm.
After formatting the SD card, you can freely copy files larger than 4GB to it. If you want to switch back to FAT32, repeat the steps above and change the file system again. Keep in mind that Windows won’t let you select FAT32 for cards larger than 32GB, and you’ll need to use Terminal or third-party software for that.
