A standard created by the ITU for compression of video for transmission over limited-bandwidth connections. H.263 has been widely adopted as the standard for video over GSM, WCDMA and some other mobile networks.

H.263 only includes the visual part of a video stream; audio must be handled separately, using a standard such as AMR.

H.263 specifies several standard image sizes, including sub-QCIF (128 x 96 pixels), QCIF (176 x 144), and CIF (352 x 288).