Will audio be preserved in the WebM?

Yes. Audio is converted to Opus or Vorbis codec — WebM's open audio formats — preserving all audio content from your original MP4.

🎬 Video Converter

MP4 to WebM Converter — Free & Private

WebM is the open, royalty-free video format built for the web. Convert your MP4 to VP9 WebM for HTML5 <video> embeds, website background loops, open-source projects, and transparent video overlays. No upload, no server, no license fees.

⚡ Convert MP4 to WebM Now Browse All Tools

✓ Free forever ✓ No upload ✓ Royalty-free output ✓ FFmpeg-powered

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100% in your browser · VP9 WebM output · Your video never leaves your device

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Why Web Developers Choose WebM Over MP4

MP4 (H.264) is everywhere, but it carries patent licensing obligations — every encoder and decoder technically owes royalties to MPEG-LA. For open-source software, government websites, and organizations committed to open standards, this is a real legal constraint. WebM, developed by Google and released in 2010, uses the VP8 and VP9 codecs under a royalty-free license — anyone can encode, decode, and distribute WebM without owing licensing fees. Beyond licensing, WebM has a unique technical capability: VP8 and VP9 support alpha channel transparency, enabling video overlays with no background. H.264 MP4 simply cannot do this. For web background video loops, WebM + MP4 dual-source is the professional standard for full browser compatibility.

🆓 Royalty-free format — VP9/VP8 are patent-free; H.264 carries MPEG-LA licensing obligations
📉 30–40% smaller files — VP9 achieves better compression than H.264 at equal quality
🔲 Transparency support — WebM supports alpha channel video; MP4/H.264 does not
🌐 Universal browser support — Chrome, Firefox, Edge, Opera, and Safari 14+ all support WebM
💻 HTML5 video best practice — dual-source WebM + MP4 gives 100% cross-browser coverage
🔒 100% private — FFmpeg.wasm converts in your browser; no video data touches a server

How to Convert MP4 to WebM

Open the Converter

Click "Convert Now" to open the video converter with MP4 → WebM pre-selected.

Load Your MP4 File

Drag & drop your MP4 or click Browse. Supports any H.264 or H.265 MP4 file.

Convert to VP9 WebM

FFmpeg.wasm re-encodes your video to VP8 or VP9 with Opus audio, entirely in your browser.

Download WebM

Your WebM file downloads automatically — ready to embed in your website or project.

Features

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100% Private

FFmpeg.wasm runs locally. Your video files never leave your device.

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Alpha Channel

Create transparent WebM video for web overlays — impossible with H.264.

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Free Forever

No account, no fee, no watermarks. Royalty-free output included.

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Smaller Files

VP9 encoding produces 30–40% smaller files than H.264 at equal quality.

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Web-Ready

Output is optimized for HTML5 video embedding and autoplay background loops.

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Opus Audio

Audio converts to Opus codec — WebM's royalty-free, high-quality audio standard.

Frequently Asked Questions

WebM is royalty-free and open-source. H.264 (MP4) requires patent licensing for encoders and decoders. For open-source projects, government sites, or organizations avoiding patent royalties, WebM is the compliant choice. WebM also achieves smaller files at equal quality using VP9.

All major browsers support WebM: Chrome, Firefox, Edge, Opera, and Safari 14+. For maximum compatibility, use both WebM and MP4 sources in your HTML: <source src="video.webm"> <source src="video.mp4">.

Yes — VP8 and VP9 WebM supports alpha channel transparency. H.264 MP4 does not. If you need transparent video overlays on a website, WebM is the only widely-supported option (alongside HEVC on Safari).

Using VP9 codec, WebM is typically 30–40% smaller than H.264 MP4 at the same quality. Encoding time is longer than H.264 because VP9 is more computationally intensive.

Drop your MP4 into the converter, select WebM output, convert, and download. Upload the WebM file to your media library alongside the MP4 for cross-browser background video.

Yes. Audio is converted to Opus codec — WebM's open audio format — preserving all audio content from your original MP4.

No. FFmpeg.wasm converts everything in your browser. Your video never leaves your device.