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; plays almost anywhere
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. It converts one video or many at once. Browse files lists only videos in the source format, but videos dropped on it can be in any of them, and each one converts from its own format, so an MKV file converts even on the MOV to MP4 converter. The Resolution, Frame Rate, Quality, and Audio options in Settings, under the target format, can make the videos smaller or drop their sound, and they leave them as they are 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 format or option clears the results until you press Convert again. When it's done, the converted videos show up in a grid. GIFs play right in the grid, and a click shows one full size. The converted files keep the original file names with the new extension.

Videos are converted on your device with FFmpeg and never uploaded. Before the first conversion, the page downloads FFmpeg.

Convert many videos at once

Pick or drop as many videos as you like, and add more at any time: this is a batch video converter, so a set of phone clips or screen recordings converts with one press of Convert, whether it's MOV to MP4, MKV to MP4, or MP4 to GIF.

  • The videos convert one after another, in the order they were added, and the progress bar counts them. Cancel stops the video converting and the ones waiting, and the videos already converted keep their results.
  • Videos added later wait for Convert, which then converts only them and any that failed.
  • The converted videos show up in a grid, each with its own Download button.
  • Download All saves every converted video in one ZIP file, or a single converted video as it is.
  • When two videos would get the same name, a number is added to the later one, as in clip (1).mp4.
  • If a video can't be converted, an error message names it, and the others still convert. Press Convert to try it again.

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, in the exact terms of the target's codec. Each value is marked High, Medium, or Low: lower ones make smaller files with a softer, blockier picture. Every target starts on its bold High value. A value the next target you pick doesn't offer becomes that target's bold value in the same group, so CRF 30 (Low) in MP4 becomes qscale 12 in AVI.

    Target High Medium Low
    MP4, MOV, MKV, FLV, 3GP (H.264 CRF) 18, 20, 23 25, 28 30, 33, 36, 40
    AVI, WMV, MPEG (qscale) 2, 3, 4 6, 8 10, 12, 16, 20, 31
    WebM (VP8 bitrate cap) 16, 12, 8 Mbps 6, 4 Mbps 3, 2, 1 Mbps, 500 kbps
    GIF (colors per frame) 256, 192 128, 96 64, 32, 16

    A lower CRF or qscale keeps more detail. GIF colors at Low are 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 the Quality it starts on (its bold High value), 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 H.264 AAC H.264 and AV1 video, AAC sound
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.
  • Video re-encoded to H.264 or VP8, for MP4, MOV, MKV, FLV, or WebM, is scaled down to fit in 4096 × 2304 pixels, or 2304 × 4096 for a video filmed upright: as many pixels as H.264's level 5.2 allows. FFmpeg in the browser doesn't have the memory to encode 8K video to H.264.
  • Re-encoded MPEG video is scaled down to fit in 1920 × 1152 pixels, the largest picture MPEG-2 defines, or 1152 × 1920 for a video filmed upright. It gets 4:2:0 color, as on DVDs.
  • Surround sound is mixed down to stereo in WMV, AVI, and MPEG files.
  • Sound is resampled when the target's codec can't take its sample rate: WMV sound gets at most 48 kHz, and MPEG sound 32, 44.1, or 48 kHz.
  • 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.
  • FFmpeg in the browser can't decode AV1 video, so AV1 converts only by copying: to MP4, MKV, or WebM, with the Resolution, Frame Rate, and Quality they start on.

Tips

  • For a video that plays almost anywhere, 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 reads the video from your device as it goes, but keeps the converted file in memory until it's done, so a very large result may not fit, especially on a device with little memory.