Private media conversion
WebM to MP4 Converter
Transcode WebM video into broadly compatible H.264 MP4 with AAC audio while keeping the file on your device.
The engine downloads once from a CDN. Your media remains on this device.
How to use the webm to mp4 converter
- STEP 1Choose a WebM file up to 200 MB.
- STEP 2Convert it locally to MP4.
- STEP 3Download the finished MP4 file.
About this tool
MP4 output makes WebM recordings easier to use in editors, presentations, messaging apps, mobile galleries, and platforms with limited WebM support.
Video is encoded to H.264 CRF 23 with yuv420p pixels, while audio becomes 160 kbps AAC and fast-start metadata improves web playback.
Processing time depends on duration, source bitrate, output format, and device performance.
Frequently asked questions
Does the converter preserve transparency?
No. Standard H.264 MP4 does not preserve the alpha transparency available in some WebM videos.
Is my WebM 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.