Multimedia file format developed by the Moving Picture Experts Group (MPEG); uses a "meta-box" format that contains time-based media, such as audio and video data, as well as metadata that describes the contents of the file.

MPEG-21 may also include DRM information for copy-protection.

Media file created with the AXMEDIS Editor; saved in a packaged content distribution format and may contain multiple types of media; may also include descriptive metadata, and DRM copy-protection information.

AXMEDIS MPEG-21 files may also be saved with an .MP21 file extension.