Convert MP4 to WebM for the web
Create WebM videos with VP9 or VP8 and Opus, ready to embed in a web page. Vidmini encodes on your own device, without uploading the file.
How it works
- 1
Choose or drop the MP4 file you want to convert.
- 2
Keep WebM as the output format (VP9 or VP8 video, Opus audio).
- 3
Click MP4 to WebM, then download the WebM file. Nothing was uploaded.
Why use WebM?
WebM is an open, royalty-free format created for the web. Every modern browser plays it natively in a <video> element, which makes it a good choice for background videos, product demos and clips embedded on your own site.
Web developers often publish a WebM version next to an MP4: browsers that support WebM pick it, the others fall back to MP4. Some open-source projects, wikis and platforms also prefer or require open formats, and WebM fits that requirement.
VP9 or VP8, with Opus audio
Vidmini writes WebM files with VP9 or VP8 video and Opus audio. VP9 is the modern choice: at the same visual quality it usually produces a smaller file than H.264, which means faster page loads. VP8 is older and less efficient, but it is supported by some older players and tools that do not handle VP9.
Opus is an open audio codec that sounds good at low bitrates, for music as well as speech.
What happens during the conversion
MP4 files almost always contain H.264 or HEVC video and AAC audio, and none of these can go inside a WebM file. So an MP4 to WebM conversion always re-encodes both tracks: the video is encoded to VP9 or VP8, and the audio to Opus. The resolution of the source is kept.
Encoding VP9 is more demanding than encoding H.264, and not every device has a hardware VP9 encoder. Expect the conversion to take longer than a simple container change, especially for long or high-resolution videos. Short web clips usually take a few seconds to a minute on a recent computer.
For background or hero videos, it often makes sense to trim the clip first with Trim Video, then open the trimmed file here to convert it.
Private and free, with no size limit set by us
The conversion runs in your browser with WebCodecs and WebAssembly. Your MP4 is never uploaded, there is no account and no watermark, and the page keeps working offline once it has loaded.
We do not set a file size limit. Output is streamed to your browser’s private storage, so desktop browsers handle multi-gigabyte files; phones are limited by free memory and storage.
Frequently asked questions
Is WebM smaller than MP4?
Often, yes, when you use VP9: it compresses more efficiently than H.264, so a WebM file can be smaller at similar quality. The exact difference depends on the content of the video.
Should I choose VP9 or VP8?
There is no codec option: Vidmini uses VP9 when your browser can encode it, for smaller files at the same quality, and falls back to VP8 otherwise.
Does MP4 to WebM lose quality?
The video has to be re-encoded, because H.264 cannot be stored in WebM. Vidmini keeps the original resolution, and the difference is usually hard to see at normal viewing sizes.
Can I embed the WebM file on my website?
Yes. Use it in an HTML <video> element. For the widest reach, offer the WebM and the original MP4 as two sources, so every browser finds a version it can play.
Why is the conversion slower than MOV to MP4?
MOV to MP4 can often copy the streams without re-encoding. MP4 to WebM always re-encodes both video and audio, and VP9 encoding needs more work, especially when no hardware VP9 encoder is available.
Is my video uploaded?
No. Everything happens in your browser. The page can only talk to vidmini.com for its own code, and no tracking cookies are used.