USB mass storage device class
USB device class for drives
The USB mass storage device class (also known as USB MSC or UMS) is a set of computing communications protocols, specifically a USB Device Class, defined by the USB Implementers Forum that makes a USB device accessible to a host computing device and enables file transfers between the host and the USB device. To a host, the USB device acts as an external hard drive; the protocol sets interfaces with a number of storage devices.
Uses
Devices connected to computers via this standard include:
External magnetic hard drives
External optical drives, including CD and DVD reader and writer drives
USB flash drives
Solid-state drives
Adapters between standard flash memory cards and USB connections
Digital cameras
Portable media players
Card readers
PDAs
Mobile phones
Devices supporting this standard are known as MSC (Mass Storage Class) devices. While MSC is the original abbreviation, UMS (Universal Mass Storage) has also become common use.
Operating system support
Most mainstream operating systems include support for USB mass storage devices; support on older systems is usually available through patches.
Microsoft Windows
Microsoft Windows has supported MSC since Windows 2000. There is no support for USB supplied by Microsoft in Windows before Windows 95 and Windows NT 4.0. Windows 95 OSR2.1, an update to the operating system, featured limited support for USB. During that time, no generic USB mass-storage driver was produced by Microsoft (including for Windows 98), and a device-specific driver was needed for each type of USB storage device. Third-party, freeware drivers became available for Windows 98 and Windows 98SE, and third-party drivers are also available for Windows NT 4.0. Windows 2000 has support (via a generic driver) for standard USB mass-storage devices; Windows Me and all later Windows versions also include support.
Begin with the source’s own compact description: “USB mass storage device class” is uSB device class for drives. The dossier treats that line as a proposition to test through mass, storage and device, not as a finished interpretation.
Why this record matters
The phrase “uSB device class for drives” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jul 4, 2026. The linked authority identifier is Q1155870. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2000.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “USB mass storage device class” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.