![1girl animated anmi bad_id bad_twitter_id bangs blinking blonde_hair blue_eyes blush brown_hair closed_mouth commentary_request girls_frontline hair_ornament korean_commentary live2d long_hair looking_at_viewer lowres mp4 out_of_frame peeking_out qquack sidelocks simple_background smile snowflake_hair_ornament solid_white_thumbnail solo suomi_kp31_(girls_frontline) white_background rating:s score:23 1girl animated anmi bad_id bad_twitter_id bangs blinking blonde_hair blue_eyes blush brown_hair closed_mouth commentary_request girls_frontline hair_ornament korean_commentary live2d long_hair looking_at_viewer lowres mp4 out_of_frame peeking_out qquack sidelocks simple_background smile snowflake_hair_ornament solid_white_thumbnail solo suomi_kp31_(girls_frontline) white_background](/cdn_image/preview/96/2a/962a793535c8927c1d0c859899a842ed.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).