Why WebM often needs transcoding
WebM commonly carries VP8, VP9 or AV1 video and Opus audio. MP4 can carry some of these combinations, but broad destination compatibility often favors AVC/AAC.
Check browser encoders
WebCodecs exposes hardware/native encoders differently by browser and operating system. The converter checks support before beginning a long transcode.
Watch transparency
Transparent WebM video is a specialized workflow. Standard MP4 delivery normally discards alpha; keep the WebM master when transparency matters.
Compare output rather than chasing an extension
A working MP4 is not automatically smaller or higher quality. Review output resolution, duration and bytes.
Official marketplace references
Requirements can change. Review the source before publishing an important listing.
Mediabunny browser media toolkit documentation ↗