Compress video

How to use the Video Compressor

1. Drop in the clips that are over the limit.
2. Choose Quality level, Target size (MB) or Percent of original.
3. For a big cut, pick a lower Resolution as well, such as 720p.
4. Compress, then check how much each clip shrank in its row of the list.

Aiming at a number of megabytes

With a size target, the clip’s duration decides the bitrate: the page sets aside room for the soundtrack plus a small safety margin and gives the rest to the picture. If the first result lands more than 2% over, it corrects the bitrate and encodes one more time, so a target-size job can take noticeably longer than a quality level.

Some targets cannot work. When the numbers leave less than about 60 kbps for the picture, the page stops and says so instead of handing back mush; trim the clip or choose a bigger target.

Graphics chip first, WebAssembly second

MP4, MOV, WebM and MKV clips go through WebCodecs, which can use your device’s video hardware: H.264 for MP4, MOV and MKV, VP9 for WebM. Certain hardware encoders refuse to go below a quality floor; when that makes the target miss, the job switches to x264 in single-thread ffmpeg.wasm, slower but accurate.

Clips in AVI, WMV, FLV and similar older containers skip the hardware step: x264 handles them directly and the result is an MP4. Along that path the soundtrack is limited to 96 kbps at most.

Never a bigger file

A clip that is already lean is returned as it was whenever re-encoding fails to beat its size. A target size at or above the current size also returns the original.

Resolution is the strongest lever: a clip shown at 720p usually looks better than the same clip squeezed to the same size at 1080p or 4K.

Questions