Convert MP4 to WebM (VP9) instantly in your browser - no upload needed
Convert MP4 to WebM for smaller, royalty-free web video. WebM pairs VP9 video with Opus audio for excellent compression and native support in the HTML video element. Everything runs in your browser - nothing is uploaded.
or click to select a file
🔒 Your files never leave your device - 100% private & secure
Drag an MP4 file onto the upload area or click Select Video.
WebM is selected automatically. Optionally adjust quality via the Advanced toggle, then click Convert. The video is re-encoded to VP9 and Opus locally. Download the WebM when done.
WebM is an open, royalty-free container built specifically for the web. It pairs VP9 video with Opus audio to deliver smaller files at the same visual quality as H.264 MP4, which means faster page loads, lower bandwidth bills and better Core Web Vitals scores. Every modern browser plays WebM natively in the HTML5 video element, so there is no plugin for your visitors to install and no licensing fee for you to worry about.
The typical use case is a developer shipping background videos, hero loops or short clips on a site and wanting them to be as light as possible. Serving WebM to browsers that support it, with an MP4 as a fallback, is a well established pattern for squeezing out every kilobyte without sacrificing quality. Because Opus is dramatically more efficient than AAC at low bitrates, the audio shrinks noticeably too.
VidShift encodes with VP9 rather than the older VP8 because VP9 compresses meaningfully better at the same quality and is now supported everywhere that matters. Audio is converted to Opus, the most efficient audio codec available in browsers. Because moving from H.264 to VP9 is always a full re-encode rather than a container swap, longer clips take real time to process, so the progress bar reports throughput and an estimated time remaining so you know what to expect for a long video.
As with every VidShift tool, the conversion happens entirely on your device using WebAssembly and WebCodecs. Your MP4 is never uploaded, there is no account and no size cap, and the output carries no watermark. If you later need to go back the other way, our WebM to MP4 converter does exactly that.
VidShift encodes WebM with VP9, which offers noticeably better compression than the older VP8 at the same quality and is supported by every modern browser and player.
WebM (VP9 + Opus) is an open, royalty-free format that produces smaller files than H.264 MP4 at equal quality and is natively supported by the HTML video element. It is the preferred choice for web developers optimising page weight.
Yes. WebM output is always re-encoded to VP9 and Opus, so it takes longer than a lossless remux. The progress bar shows throughput so you can gauge how long a long clip will take.
No. Conversion runs entirely in your browser using WebAssembly and WebCodecs, so your MP4 file never leaves your device.