What is an SD card? Here's what you need to know about the small memory cards for electronic devices

Posted by Sherie Connelly on Wednesday, June 19, 2024

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  • SD cards are small thumbnail-sized memory storage cards. 
  • There are several varieties of SD cards available today with max capacities ranging up to 128 TB. 

An SD card, short for Secure Digital card, is a type of removable memory card used to read and write large quantities of data in a wide variety of mobile electronics, cameras, smart devices, and more. 

It has become the default standard of memory card for most consumer electronics (though a smaller version, the Micro SD card, is commonly used in phones and other devices where physical space is more of a premium). 

What to know about SD cards

The SD card debuted in 1999 and is the successor to the now-obsolete MultiMediaCard (MMC). It was one of a number of competing memory card formats in use by consumer electronics, such as Sony's defunct Memory Stick and the CompactFlash card, which, while still in use, is much less common than it was in decades past. 

The SD card is about the size of an average thumbnail. Dave Johnson/Business Insider

As the electronics industry has evolved, the original SD card specification has been updated several times to allow for higher capacities. That means there are several types of SD cards sold and used today:

  • SD: The original SD card is no longer produced. It had a maximum capacity of 2 GB and used the FAT16 file system.
  • SDHC: The Secure Digital High Capacity (SDHC) card debuted in 2006. It supports capacities up to 32 GB and uses the FAT32 file system.
  • SDXC: The Secure Digital eXtended Capacity (SDXC) format got its start in 2009. It can store up to 2 TB on the exFAT file system.
  • SDUC: Secure Digital Ultra Capacity (SDUC) cards appeared in 2018 and can support 128 TB per card using exFAT. 

Common uses for SD cards

Due to their relatively small size, SD cards have been widely adopted in an array of consumer electronics for inexpensively storing gigabytes of data. They're found in digital cameras, video game consoles, set-top boxes, and home theater devices like Blu-ray players, as well as smart home/Internet of Things devices like security cameras. While early smartphones used SD cards, most phones have migrated to the smaller Micro SD card format. 

SD cards are used in a vast array of consumer electronics — everything from cameras to laptops to video game consoles. nicolas_/Getty Images

Because of the popularity of SD cards, many desktop computers and laptops have an SD card reader built in; for those that don't, there are inexpensive USB hubs and media card readers that attach to an available USB port.

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Dave Johnson Freelance Writer Dave Johnson is a technology journalist who writes about consumer tech and how the industry is transforming the speculative world of science fiction into modern-day real life. Dave grew up in New Jersey before entering the Air Force to operate satellites, teach space operations, and do space launch planning. He then spent eight years as a content lead on the Windows team at Microsoft. As a photographer, Dave has photographed wolves in their natural environment; he's also a scuba instructor and co-host of several podcasts. Dave is the author of more than two dozen books and has contributed to many sites and publications including CNET, Forbes, PC World, How To Geek, and Insider. Read more Read less

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