A memory card or flash memory card is a solid-state electronic flash memory data storage device capable of storing digital contents. These are mainly used with digital cameras, handheld and Mobile computers, mobile phones, music players, video game consoles, and other electronics. They offer high re-record-ability, power-free storage, small form factor, and rugged environmental specifications. There are also non-solid-state memory cards that do not use flash memory, and there are different types of flash memory.

There are many different types of memory cards and jobs they are used for. Some common places include in digital cameras, game consoles, cell phones, and industrial applications. PC card (PCMCIA) were among first commercial memory card formats (type I cards) to come out in the 1990s, but are now only mainly used in industrial applications and for I/O jobs (using types I/II/III), as a connection standard for devices (such as a modem). Also in 1990s, a number of memory card formats smaller than PC Card came out, including CompactFlash, SmartMedia, and Miniature Card. In other areas, tiny embedded memory cards (SID) were used in cell phones, game consoles started using proprietary memory card formats, and devices like PDAs and digital music players started using removable memory cards.

From the late 1990s into the early 2000s a host of new formats appeared, including SD/MMC, Memory Stick, xD-Picture Card, and a number of variants and smaller cards. The desire for ultra-small cards for cell-phones, PDAs, and compact digital cameras drove a trend toward smaller cards that left the previous generation of "compact" cards looking big. In digital cameras SmartMedia and CompactFlash had been very successful, in 2001 SM alone captured 50% of the digital camera market and CF had a strangle hold on professional digital cameras. By 2005 however, SD/MMC had nearly taken over SmartMedia's spot, though not to the same level and with stiff competition coming from Memory Stick variants, xD, as well as CompactFlash. In industrial fields, even the venerable PC card (PCMCIA) memory cards still manage to maintain a niche, while in cell-phones and PDAs, the memory card market is highly fragmented.

Nowadays, most new PCs have built-in slots for a variety of memory cards; Memory Stick, CompactFlash, SD, etc. Some digital gadgets support more than one memory card to ensure compatibility.

Since many EEPROM devices only allow a limited number of write cycles, some of these cards incorporate wear levelling algorithms to spread the wear and to avoid wearing out specific places which are often written to.

Overview of all memory card types

main: Comparison of memory cards

• PCMCIA ATA Type I Flash Memory Card (PC Card ATA Type I) (max 8 GB (8 GiB) flash as of 2005)
• PCMCIA Linear Flash Cards, SRAM cards, etc.
• PCMCIA Type II, Type III cards
• CompactFlash Card (Type I), CompactFlash High-Speed (max 32 GB as of 2008)
• CompactFlash Type II, CF+(CF2.0), CF3.0
• Microdrive (max 6 GB as of 2005)
• MiniCard (Miniature Card) (max 64 MB (64 MiB))
• SmartMedia Card (SSFDC) (max 128 MB) (3.3 V,5 V)
• xD-Picture Card, xD-Picture Card Type M
• Memory Stick, MagicGate Memory Stick (max 128 MB); Memory Stick Select, MagicGate Memory Stick Select ("Select" means: 2x128 MB with A/B switch)
• SecureMMC
• Secure Digital (SD Card), Secure Digital High-Speed, Secure Digital Plus/Xtra/etc (SD with USB connector)
• miniSD Card
• microSD Card (aka Transflash, T-Flash)
• SDHC
• MU-Flash (Mu-Card) (Mu-Card Alliance of OMIA)
• C-Flash
• SIM card (Subscriber Identity Module)
• Smart card (ISO 7810 Card Standard , ISO 7816 Card Standard, etc.)
• UFC (USB FlashCard) 1 (uses USB)
• FISH Universal Transportable Memory Card Standard (uses USB)
• Disk memory cards:
• Clik! (PocketZip), (40 MB PocketZip)
• Floppy disk (LS120, 2-inch, 3.5-inch, etc.)
• Intelligent Stick (iStick, a USB-based flash memory card with MMS)
• SxS (S-by-S) memory card, a new memory card specification developed by Sandisk and Sony. SxS complies to the ExpressCard industry standard. 2
• Nexflash Winbond Serial Flash Moduel (SFM) cards, size range 1 mb, 2 mb and 4 mb.