Card Reader

A card reader is a hardware device that reads and writes various flash memory card formats. Some computers (particularly laptops) may include built-in card readers, but they are more common on other devices like printers, scanners, digital cameras, and audio recorders. Computers without a built-in card reader can use external USB-connected card readers. An external card reader that uses USB-C can even connect to smartphones and tablets to allow them to transfer data to and from memory cards.

External card readers often include multiple slots, each designed for a different type of memory card. SD and microSD cards are the most widely used, but other formats like Compact Flash, XQD, CFexpress, and Memory Stick cards are also commonly found on multi-card readers.

Inserting a card into a computer's card reader automatically mounts that card's contents. Once mounted, it appears like any other disk connected to the computer and is accessible through File Explorer (on Windows) or the Finder (on macOS). Since most digital cameras use memory cards to save and transfer digital photos, your computer may even automatically launch photo management software to import photos when a memory card is connected. Like with any other type of removable disk, memory cards in a card reader should be unmounted (or "ejected") before you remove the card; this stops all read-and-write activity and prevents corruption of the card's data.

NOTE: Since Windows automatically mounts memory cards once connected, a memory card containing malware could infect your computer. You should never connect an unfamiliar memory card to your computer if you're unsure of its contents.