Audio description is a service or feature of the auditory modality that contains an oral narration with details or context involving situations and scenes found in an audiovisual content (such as recorded video presentations, broadcast television, cinema, live or recorded drama). The primary users of audio description are blind persons or persons with low vision and their friends and family. ITU-T T.701.21 provides guidance to audio description developers and practitioners in creating effective content describing audiovisual material in an auditory-only modality, the style or manner in which audio description is delivered, the audio description script and script time cues, in relation to the original content. ITU-T T.701.21 is a technically aligned text with ISO/IEC TS 20071-21:2015, "Information technology – User interface component accessibility – Part 21: Guidance on audio descriptions".