![1girl ^_^ animal_ears animated bakemonogatari bare_shoulders breasts brooch brown_hair cleavage closed_eyes collarbone dithering dress evandragon eyebrows eyebrows_visible_through_hair fangs gif_artifacts hands_up happy head_tilt imaizumi_kagerou jewelry jpeg_artifacts layered_dress long_hair long_sleeves looking_at_viewer monogatari_(series) mp4 nekomonogatari off_shoulder open_mouth parody pout solo swaying talking touhou upper_body white_background wolf_ears rating:s score:31 post #2410754](/cdn_image/preview/44/ce/44ce2fcee95a2d2c0b8334152ff6805f.jpg)
MPEG-4 Part 14 or MP4 is a multi-purpose container format based on Apple's QuickTime format. It is an ISO standard (ISO/IEC 14496-14). It can be used for audio as well as video. It is mostly used to contain H.264 (MPEG-4 Part 10) compressed video with/and/or AAC (Advanced Audio Coding) or MP3 compressed audio. Modern browsers can directly stream MP4 files.
H.264 is the most used video format for video streaming while AAC is the successor to MP3, being more efficient than its predecessor. MP3 is still by far the most used audio format.
This tag implicates animated (learn more).