A memory card is a storage device for saving digital photographs. It is small, removable, and rewritable. The most common types are SD cards, used in most consumer cameras, and CFexpress cards, used in professional cameras. Memory cards come in different capacities, from a few gigabytes to over a terabyte. They also come in different speeds, measured in megabytes per second. Speed matters for burst shooting and video recording. A slow card can bottleneck a fast camera.

Memory cards are not all the same. SD cards have speed classes: Class 2, 4, 6, 10, UHS-I, UHS-II, and UHS-III. The higher the class, the faster the card. CFexpress cards use PCIe interfaces and are much faster. Card reliability matters. A corrupted card can lose a day's work. Photographers often use two cards in cameras with dual slots, writing to both simultaneously as a backup. Cards should be formatted in the camera, not on a computer, to avoid compatibility issues. They should be stored safely and replaced every few years.

Memory card types

• SD. Most common, used in consumer cameras.
• MicroSD. Smaller, used in phones and action cameras.
• CFexpress. Fast, used in professional cameras.
• XQD. Older format, similar to CFexpress.

A memory card is not a permanent archive. It is a temporary storage device. Images should be backed up to a computer or cloud service as soon as possible.