Compress WebM
Opens with the WebM format selected. Switch to MP4 under Advanced if you need it.
On this page Advanced is open and Format is set to WebM (VP9 video). When you load a file, the target size is computed from its resolution, frame rate and length. Tap 70%, 50%, 30% or 10%, or click the After size and type a number in MB, to aim for a different size.
Free Video Compressor
No sign-up. No upload. No size limit.
Nothing is uploaded — the file is compressed on your device.
Where large WebM files come from
Browser-based screen recorders and some capture tools save WebM. The size depends on the bitrate the recorder chose, and a recorder has to encode live, while you record.
This page plans VP9 at 70% of the bitrate it would give H.264 for the same picture size. For 1080p at 30 fps that is about 2.8 Mbps; for 720p at 30 fps, about 1.3 Mbps. The bitrate is never set higher than the source's own. If the WebM already uses less, the panel shows "At this setting the file stays about the same size."
Stay WebM or switch to MP4
Format lists MP4, MP4 · HEVC, WebM and WebM · AV1, but only the ones this browser can encode on this device. If your device cannot encode VP9, WebM cannot be selected and the page switches to the first format in the list that it can encode. WebM · AV1 is planned at 55% of the H.264 bitrate. Some upload forms accept MP4 but not WebM; for those, set Format to MP4.
WebM holds Opus or Vorbis audio. With Audio set to Keep as is and WebM output, an Opus or Vorbis track is copied; any other audio is re-encoded to Opus at its own bitrate, up to 128 kbps. For MP4 output, 128 kbps or 64 kbps re-encodes the sound to AAC. If the browser cannot decode the audio partway through, compression restarts, the original audio is kept as it is and a note under the result says so.
Long recordings
WebM files of several GB work, because the output is written to disk as it is produced. Once the page has loaded it needs no network: the file is read and compressed on your device. Only the first audio track is kept, and audio with more than 2 channels is mixed down to stereo when re-encoded. To keep only part of a recording, use Trim Video ↗; for a still image from it, Video Frame ↗.
Frequently asked questions
Can I turn a WebM into an MP4 here?
Yes. Set Format to MP4 under Advanced. Pick 128 kbps under Audio to get AAC sound.
Why can't I choose WebM?
This browser cannot encode VP9 on this device, so the page does not offer it.
Which gives the smaller file at the same resolution, WebM or MP4?
This page plans WebM (VP9) at 70% of the MP4 (H.264) bitrate, and WebM · AV1 at 55%. At a fixed target size, the codec with the lower planned bitrate can keep a higher resolution for longer clips.
Is the original WebM changed?
No. The result is a new file ending in "-compressed.webm" (or ".mp4").
Compress WebM
Opens the compressor with a target size computed for this page.