Convert MP4 to WebM for the Web

xFormat converts MP4 to WebM (VP9 video, Opus audio) in your browser, giving you web-ready video files without uploading anything to a server.

Runs in your browser — files never leave your device.

How it works

WebM is an open format built for the web and often produces smaller files than MP4 at similar quality. Use this tool to prepare background videos, product demos and short clips for your site, entirely on your own device.

1
Choose the MP4 file you want to embed.
2
Select WebM as the output format.
3
Click Convert and download the WebM file.

Why use WebM on a website?

WebM with VP9 video and Opus audio is open and royalty-free, and it compresses efficiently, so pages load faster and use less bandwidth. It works in the <video> tag of current Chrome, Firefox, Edge and Safari. Older Safari and iOS versions may not support it, so a common approach is to list both: WebM first, then your original MP4 as a fallback source.

Expect a re-encode

MP4 files normally contain H.264 video and AAC audio, which cannot be placed into a WebM container. Conversion therefore decodes and re-compresses the video as VP9 and the audio as Opus. That takes longer than a container swap, and each lossy generation costs a little quality, so start from your best original rather than an already-compressed copy.

Your browser's hardware-accelerated encoders are used when the device supports them. If they cannot handle the file, compatibility mode runs instead, with a one-time download of around 31 MB. That mode encodes VP8 video and Vorbis audio, because VP9 encoding is not reliable there.

Practical tips

Trim and compress long clips first with the other xFormat tools if you only need a short loop. Keep source files within about 500 MB on desktop and 200 MB on phones.

Frequently asked questions

Is WebM smaller than MP4?

Often, at similar visual quality, since VP9 is generally more efficient than H.264. The exact saving depends on the content, so compare the output with your original.

Does WebM work in Safari and on iPhone?

Current Safari versions support WebM, but older ones may not. If you must cover older devices, offer an MP4 fallback in your video tag.

Can I convert MP4 to WebM without losing quality?

No. The codecs differ, so the video is re-encoded and some loss is unavoidable, though it is usually hard to notice at reasonable settings.

Is my video uploaded?

No. The conversion happens locally in your browser and the file stays on your device.

Does it work on mobile?

Yes, but keep files under about 200 MB, and expect slower encoding than on a desktop.