WebM with VP9 is the royalty-free, highly efficient format built for HTML5 video. It produces small files that stream well, making it ideal for backgrounds and embedded web video. This tool re-encodes your clips to WebM. For device playback, MP4 remains the universal default.
Why VP9 WebM loads faster on websites
WebM pairs the VP9 video codec with Vorbis or Opus audio, and the combination is built specifically for HTML5 delivery. VP9 squeezes a given level of visual quality into noticeably smaller files than H.264, which means quicker page loads, less bandwidth on your CDN bill, and smoother autoplay for muted background loops. Because WebM is royalty-free, you can ship it on commercial sites without licensing worries. It is the format YouTube serves to compatible browsers for exactly these reasons. Drop a WebM into an HTML5 <video> tag, list an MP4 as a fallback source, and you cover both efficiency and reach. The trade-off is encoding time: VP9 is slower to compress than H.264, so larger clips take longer to process.
WebM for the web, MP4 and MOV for everything else
WebM shines in the browser but is the wrong pick for offline playback and Apple-centric workflows. Safari's WebM support arrived late and remains patchy on older macOS and iOS versions, and many TVs, editors, and phone gallery apps simply won't open it. For those cases reach for MP4, the universal default, or MOV when you need a QuickTime-native file for Final Cut Pro. A common pattern is to keep two encodes: a small WebM for fast website streaming and an H.264 MP4 fallback so every visitor sees something. HD Video Converter can produce both from the same source.