FFmpeg supports a wide range of video formats (also called containers). Below is a list of commonly used types, their extensions, and general use cases.

Format	Extension	Common Codecs	Use Case
MP4	.mp4	H.264, AAC	Web video, mobile devices, streaming
AVI	.avi	Xvid, MJPEG	Legacy compatibility, Windows apps
MKV (Matroska)	.mkv	H.264, VP9, Opus	High-quality storage, subtitles, multiple tracks
WebM	.webm	VP8/VP9, Opus	Web use, HTML5 video
MOV	.mov	H.264, ProRes	Apple ecosystem, professional editing
FLV	.flv	H.263, MP3	Legacy Flash video
OGG	.ogv	Theora, Vorbis	Open source video, browser support
MPEG-TS	.ts	MPEG2, H.264	Broadcasting, streaming segments

Changing Output Format in fluent-ffmpeg

ffmpeg('input.avi')
  .format('mp4')        // Convert to MP4
  .save('output.mp4');

Listing Supported Formats

const ffmpeg = require('fluent-ffmpeg');

ffmpeg.getAvailableFormats((err, formats) => {
  console.log(formats);
});

Note: This returns an object where each key is a format code (e.g. mp4, avi, mkv), with descriptions and flags.