Private media conversion
MP4 to WebM Converter
Transcode MP4 video into a modern VP9 WebM with Opus audio entirely on your device.
The engine downloads once from a CDN. Your media remains on this device.
How to use the mp4 to webm converter
- STEP 1Choose a MP4 file up to 200 MB.
- STEP 2Convert it locally to WebM.
- STEP 3Download the finished WebM file.
About this tool
WebM is designed for web delivery and uses open VP9 and Opus codecs supported by modern browsers and many web platforms.
The converter uses VP9 constant-quality encoding at CRF 32 and 128 kbps Opus audio. VP9 can be computationally intensive on longer videos.
Processing time depends on duration, source bitrate, output format, and device performance.
Frequently asked questions
Will WebM be smaller than MP4?
Often, but not always. File size depends on the source, motion, duration, and codecs; this tool prioritizes a practical constant-quality VP9 encode.
Is my MP4 file uploaded?
No. FFmpeg WebAssembly performs the conversion in your browser. The engine downloads from a CDN, but your media stays on your device.
What is the maximum file size?
The browser converter accepts files up to 200 MB. Long files may require substantial device memory.