Convert and compress video
Transcode MP4, WebM, MKV, MOV and AVI, trim, compress, change resolution or frame rate, extract the audio track or export an animated GIF.
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Accepts MP4, WebM, Matroska (MKV), QuickTime (MOV), AVI. Up to 3 files at once, 100 MB each.
Free · up to 3 files · 100 MB each · files deleted automatically after 1 hour.
How video conversion works here
The extension is the box, not the contents
MP4, MOV, MKV, AVI and WebM are containers. A container records how the streams inside a file are packed together and kept in sync; it does not describe how the video is compressed. What decides how a video looks, how large it is, and whether it plays at all is the codec stored inside.
That is why two files both ending in .mp4 can behave completely differently, and why the useful question when a video will not play is never about the extension. It is almost always the codec.
What your converted file will actually contain
MP4, MOV and MKV are written with H.264 video and AAC audio — the combination with the broadest support of anything in current use. MP4 additionally gets its index moved to the front of the file so playback can begin before the download finishes.
WebM is written with VP9 and Opus, both royalty-free, which is the reason the format exists. VP9 encodes considerably slower than H.264, so expect a longer wait for the same clip. AVI is written with MPEG-4 Part 2 and MP3, the codecs it was designed around — roughly a generation behind, which means an AVI is usually larger than an MP4 of the same clip at the same quality, not smaller.
This is a re-encode, not a repackage
Some tools can lift a stream out of one container and drop it into another untouched when the codecs happen to line up. We do not. Every job here is decoded and encoded again, so a conversion takes time in proportion to the length of the file and costs a small amount of quality even where a repackage would have been possible.
What you get in exchange is predictability. The output contains the codecs we chose rather than whatever the source happened to hold, so it plays where you expect it to — which is usually the whole reason for converting a video in the first place.
Guides on video
MP4, MOV and MKV are not really video formats
The extension on a video file tells you far less about it than most people assume. Understanding the difference between a container and a codec explains almost every confusing thing about video conversion.
7 min read
GIF is a terrible video format, and sometimes the right one
A three-second GIF can be larger than the minute-long video it came from. Here is why that happens, and the narrow set of cases where GIF still wins anyway.
5 min read