Convert MP4 to WebM Online Free
Convert to WebM lets you convert MP4 to WebM online free — turn an MP4, MOV, MKV, or AVI clip (or an audio file) into a compact .webm file right in your browser. There is no upload, no sign-up, and no account: your file is converted on your own device using WebAssembly, so it never leaves your phone or computer. Keep or drop the audio track, and the WebM downloads straight to you — free and watermark-free.
Add an MP4, MOV, MKV, or audio file above, choose whether to keep the audio, and the WebM downloads straight to you — converted on your device, watermark-free.
Got a file to convert? It only takes a moment.
Convert to WebM free →How to Convert a Video to WebM Online
Here is how to convert a video to WebM in three steps — the same on desktop, iPhone, and Android:
- Open capsuletools.app/convert-to-webm/ and tap Select a file to choose an MP4, MOV, MKV, AVI, or audio file (up to 500 MB).
- Leave the default to keep the sound, or flip the Remove audio track switch to drop the audio and shrink the file.
- Tap Convert to WebM, wait for the progress bar, then tap Save WebM to download your finished file.
That is all there is to how to convert MP4 to WebM — no software to install, no watermark, and nothing uploaded to a server. The result screen shows how much smaller your WebM is than the original.
WebM Converter — Free Online, No Upload
Most online converters send your video to their servers, make you wait in a queue, and cap how many files you can convert. This WebM converter is free and fully online, but it works differently: it runs FFmpeg compiled to WebAssembly directly in your browser, so the conversion happens on your device. Nothing is uploaded, there is no sign-up, and there are no daily limits. Very large files (above 150 MB) simply take longer and use more memory, with a 500 MB ceiling so a browser tab can hold the whole job. You can even install the tool to your home screen and use it like a native app.
Supported Formats: MP4, MOV, MKV, AVI, WAV, MP3 to WebM
The tool reads the common video and audio formats and turns each into a standard WebM file:
- MP4 to WebM — the most common video format, used by most cameras, phones, and screen recorders.
- MOV to WebM — the format the iPhone and many cameras record in.
- MKV and AVI to WebM — convert Matroska and older AVI video to the web-friendly WebM container.
- WAV and MP3 to WebM — audio-only files are encoded to a WebM audio file using the Opus codec.
- MP4
- MOV
- MKV
- AVI
- M4V
- WAV
- MP3
- M4A
- AAC
- OGG
- FLAC
- → WebM
WebM Video, the VP8 Codec, and Audio
A WebM file wraps a video codec plus an audio codec — this tool lets you convert to WebM VP8, pairing VP8 video with Vorbis audio, the most widely compatible WebM combination, playing natively in Chrome, Firefox, Edge, and modern Safari with no plugin. VP8 also encodes efficiently right in the browser, so a conversion finishes in seconds to a few minutes depending on the clip's length and resolution.
- Keep the audio — the default. The soundtrack is re-encoded to Vorbis and muxed into the WebM alongside the VP8 video.
- Remove audio track — flip the switch to drop the sound entirely and shrink the file further, useful for silent background clips and looping web animations.
- Audio-only files — a WAV or MP3 with no video is converted to a WebM audio file using the Opus codec.
Every conversion produces a standard .webm file that plays natively in every modern browser — no plugin, no extra step.
Frequently Asked Questions
Is Converting MP4 to WebM Free, With No Sign-Up?
Yes. This is a completely free MP4 to WebM converter with no sign-up, no account, and no watermark. There is no upload either — your file is converted entirely in your browser using WebAssembly, so it never leaves your device. Convert as many files as you like.
Which File Formats Can I Convert to WebM?
You can convert the common video formats — MP4, MOV, MKV, AVI, and M4V — to WebM, plus audio files such as WAV, MP3, M4A, AAC, OGG, and FLAC. Video files become a WebM video (VP8 video with Vorbis audio); audio-only files become a WebM audio file using the Opus codec. Files up to 500 MB are supported.
What Format Is WebM?
WebM is an open, royalty-free video format built for the web. It stores VP8 or VP9 video with Vorbis or Opus audio in a Matroska-based container, and plays natively in Chrome, Firefox, Edge, and modern Safari with no plugin. This converter outputs VP8 video with Vorbis audio — the most widely compatible WebM pairing — and encodes audio-only files with Opus.
Is WebM Better Than MP4?
WebM is an open, royalty-free format built for the web, and at the same quality a WebM is often smaller than an equivalent H.264 MP4 — which makes pages load faster and saves bandwidth. MP4 has broader device support, especially on older hardware and Apple platforms. WebM is the better choice for websites and open-source projects; MP4 is safer for universal playback.
Does WebM Support Audio?
Yes. WebM carries audio alongside video — this converter pairs the VP8 video with Vorbis audio automatically. You can also tick Remove audio track to drop the sound and make the file smaller, or convert an audio-only file into a WebM audio file (Opus) on its own.
