Why convert a video?

A video file is a container, named by its extension, that holds a picture and a sound track, each compressed with a codec. A program, phone, TV, or website plays the file only if it supports both the container and the codecs. Converting puts the video into a container and codecs that play where you need them.

Format Good for
MP4 Sharing and uploading; the most widely supported video format
MOV Apple devices and software
WebM Videos on web pages
MKV Films and series in media players such as VLC
AVI Older Windows programs and players that support Xvid
GIF Short silent loops; shows anywhere an image can
WMV Windows Media Player and older Windows programs
FLV Older Flash video players
MPEG DVD authoring and older players
3GP Older mobile phones

Tool description

This tool converts videos between MP4, MOV, WebM, MKV, AVI, WMV, FLV, MPEG, and 3GP, and to and from animated GIF. Every video converter here works the same way, from the general Video Converter to the ones for a single pair, such as MOV to MP4 or MP4 to GIF: it starts on the formats in its name, and the Source and Target menus switch to any other. Browse file lists only videos in the source format, but a video dropped on it can be in any of them: the source format follows the file, so an MKV file converts even on the MOV to MP4 converter. Under the target format, the Resolution, Frame Rate, Quality, and Audio options in Settings can make the video smaller or drop its sound, and they leave it as it is to begin with. Then press Convert. The progress bar shows while FFmpeg loads and how far the conversion has got, and Cancel stops it. Picking another file, format, or option clears the result until you press Convert again. When it's done, check the preview under the buttons, or scrub through it on the timeline below, and download the converted file, which keeps the original file name with the new extension.

Videos are converted on your device with FFmpeg and never uploaded. Before the first conversion, the page downloads FFmpeg, which is about 30 MB.

Options

  • Resolution scales the video down until its shorter side has that many pixels, keeping its shape: at 720p, a 1920 × 1080 video becomes 1280 × 720, and one filmed upright becomes 720 × 1280. A video that is already as small keeps its size, as scaling it up would only make a bigger file. Original keeps the size.
  • Frame Rate (fps) drops frames until the video has at most that many per second. A video with fewer keeps its own, and Original keeps them all.
  • Quality sets how much detail the picture keeps when it's re-encoded. Medium and Low make smaller files with a softer, blockier picture. A GIF gets fewer colors instead: 256 for each frame at High, 128 at Medium, and 64 at Low, where they're no longer dithered.
  • Audio keeps the sound or removes it.
  • GIF as the target starts the Resolution at 360p and the Frame Rate at 10, which keep a GIF small. Picking another target sets them back to Original. A GIF has no sound, so its Audio is set to Remove.

How it works

FFmpeg, compiled to WebAssembly, runs in your browser. It takes the first video track and the first audio track of the file and writes them in the target format:

  • When the video already uses a codec the target format holds, and the options keep its resolution, frame rate, and High quality, it's copied as it is. So is the sound when the target format holds its codec. Copying is much faster than re-encoding and loses no quality.
  • Otherwise it's re-encoded, which takes longer. FFmpeg uses one processor core in the browser. A lower resolution or frame rate makes it faster.
Target Video codec Sound codec Copied as they are
MP4, MOV, FLV H.264 AAC H.264 video, AAC sound
MKV H.264 AAC H.264, H.265, VP8, VP9, and AV1 video; AAC, MP3, AC-3, Opus, Vorbis, and FLAC sound
WebM VP8 Vorbis VP8, VP9, and AV1 video; Vorbis and Opus sound
AVI MPEG-4 Part 2 (Xvid) MP3 MPEG-4 Part 2 video, MP3 sound
WMV Windows Media Video 8 Windows Media Audio 2 The same codecs
MPEG MPEG-2 MPEG Audio Layer II MPEG-2 video, MP2 sound
3GP H.264 Baseline AAC AAC sound
GIF GIF No sound Nothing
  • A phone may store a video filmed upright as a sideways picture with a rotation flag. MP4 and MOV keep that flag, so such a video can still be copied into them. The other formats get it re-encoded and turned upright.
  • H.264 and WMV need an even width and height, so a video with an odd one loses its last row or column of pixels.
  • Each frame of a GIF gets its own palette of the colors that suit it best. A GIF gets at most 50 frames per second, so a faster video is brought down to 50.
  • A 3GP file is made for older phones: it's scaled down to fit in 640 × 480 pixels and gets at most 30 frames per second, even when the options allow more.
  • Surround sound is mixed down to stereo in WMV, AVI, and MPEG files, whose sound codecs hold two channels at most.
  • Subtitles, other audio tracks, and cover art are left out.
  • MPEG files are saved with the .mpg extension, as an MPEG-2 program stream like the files on a DVD.
  • Browsers can't play AVI, WMV, FLV, or MPEG, so when the target is one of them, the preview shows the original video instead. Some browsers can't play MOV, MKV, or 3GP, and the player then says so.

Tips

  • For a video that plays everywhere, convert to MP4.
  • To make a video smaller, lower the Quality or the Resolution.
  • H.265 (HEVC) video is re-encoded to H.264 for MP4 and MOV. MKV copies H.265 as it is, which is much faster, for players that support it.
  • Keep GIFs short, and lower the Resolution or Frame Rate for a smaller file.
  • FFmpeg keeps the whole video and the converted file in memory, so a very large video may not convert, especially on a device with little memory.