Video Converters
MP4 to WebM
Runs in your browser — files never leave your device.
Drop MP4, MOV, MKV files here
or click to browse · paste from clipboard · up to 4000 MB each
Select filesOptions
Why convert MP4 to WebM
VP9 compresses more efficiently than H.264, and WebM is royalty-free, which is why YouTube serves it. A site that hosts its own video saves bandwidth and loads faster with WebM, keeping MP4 as the fallback for old devices.
Encoding happens in your browser with the WebCodecs VP9 encoder. It is slower than remuxing — expect roughly real time for 1080p on a modern laptop.
How it works
- Drop MP4, MOV, MKV files onto the box above, click it to browse, or paste from the clipboard.
- Adjust the options if you need to — the defaults suit most cases.
- Press Convert. The work happens on your device, so speed depends on your computer or phone.
- Download the WebM — individually or all at once.
About the formats
MP4 · MPEG-4 Part 14 video · .mp4
The video format that works everywhere: phones, TVs, browsers, social networks. Normally H.264 video with AAC audio.
- MP4 is a container; the codec inside (H.264, HEVC/H.265, AV1) decides what can play it.
- H.264 MP4 is the safe choice for uploads and sharing; HEVC MP4 from newer iPhones needs extra codecs on Windows.
- The “moov atom” placement decides whether a browser can start playing before the whole file downloads.
MOV · QuickTime movie · .mov
Apple’s QuickTime container, the default for iPhone videos and Mac screen recordings; very close to MP4 but not accepted everywhere.
- MOV and MP4 share the same underlying structure, so MOV to MP4 usually only needs repackaging, not re-encoding.
- iPhone MOV files are often HEVC (H.265) with HDR, which Windows and many web apps cannot play without conversion.
- Screen recordings on Mac are MOV with H.264 and can be very large.
MKV · Matroska video · .mkv
An open container that can hold any codec plus multiple audio tracks, subtitles and chapters; popular for rips and downloads, unsupported by iPhone and many TVs.
- MKV to MP4 keeps the video quality when the codec is H.264 or HEVC — only the container changes.
- MP4 cannot carry every MKV feature: soft subtitles and some audio codecs (e.g. DTS) must be converted or dropped.
- Most desktop players (VLC, MPV) play MKV; Safari, iOS and PowerPoint do not.
WebM · WebM video · .webm
The royalty-free web video format (VP8/VP9/AV1 video, Vorbis/Opus audio) produced by browser screen recorders, Discord and many online tools.
- WebM is based on Matroska and plays in every browser, but not in iMovie, Premiere or on most phones without conversion.
- Browser recording APIs output WebM, which is why screen recordings from web apps come as .webm.
- WebM to MP4 requires re-encoding the video, because MP4 does not carry VP9 widely.
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