H.263, H.264 (or MPEG-4 Part 10 Advanced Video Coding or MPEG-4 AVC) are video compression formats used for the recording, compression, and distribution of video content as well as audio and metadata such as subtitles or closed captioning. H.263 was developed by the ITU-T Video Coding Experts Group (VCEG) in 1996. The first version of H.264 was completed in May 2003, and various extensions of its capabilities have been added in subsequent editions.

H.263 was originally designed for use in videoconferencing, but as H.264 provides significant improvement in capability beyond H.263, the H.263 standard is now considered a legacy design. Most new videoconferencing products now include H.264 as well as H.263 and H.261 capabilities.

H.264 (MPEG-4 AVC) is a block-oriented motion-compensation-based video compression standard developed by VCEG together with the ISO/IEC/JTC1 Moving Picture Experts Group (MPEG). H.264 is best known as being one of the video-encoding standards for Blu-ray Discs. It is also widely used by streaming internet sources, such as videos from Vimeo, YouTube, and the iTunes Store, web software such as the Adobe Flash Player and Microsoft Silverlight and also various HDTV broadcasts over terrestrial, cable and satellite.

The intent of the H.264/AVC project was to create a standard capable of providing good video quality at substantially lower bitrates than previous standards without increasing the complexity of design so much that it would be impractical or excessively expensive to implement and to provide flexibility to allow the standard to be applied to a wide variety of applications allowing for convenient file-sharing for such uses as archiving and transcription of original video.

The H.264 video format has a broad application range that covers all forms of digital compressed video from low bitrate Internet streaming applications to HDTV broadcast and Digital Cinema applications with nearly lossless coding. To ensure compatibility and problem-free adoption of H.264 AVC, many standards bodies have amended or added to their video-related standards so that users of these standards can employ H.264 AVC.

The Digital Video Broadcast project (DVB) approved the use of H.264 AVC for broadcast television in 2004. The Advanced Television Systems Committee (ATSC) standards body in the United States approved the use of H.264 AVC for broadcast television in 2008, although the standard is not yet used for fixed ATSC broadcasts within the United States. It has also been approved for use with the more recent ATSC-M/H (Mobile/Handheld) standard, using the AVC and SVC portions of H.264. H.264 is also used as part of recording formats by Sony, Panasonic, Canon and Nikon as well as in closed circuit TV and video surveillance products.