MP4 to WebM Converter – Free Online

How to Convert MP4 to WebM Online

Drop your MP4 file

Drag and drop your .mp4 file onto the box above, or click Choose Files. The request is already filled in: “Convert this to WebM”.

Say how, if you want

The AI assistant uses sensible defaults. To choose the resolution, frame rate or bitrate yourself, say so in the request, for example “Convert this to WebM in 720p”.

Save your WebM file

The assistant opens with your file and converts it on your own device; the file itself is never uploaded. When the WebM file is ready, click Save. Prefer to set everything by hand, or batch-convert several files into a ZIP? The classic converter is one click away on this page.

Why Convert MP4 to WebM?

WebM with VP9 video typically achieves the same quality as H.264 MP4 at 20 to 40% smaller files, which is why YouTube and most modern websites serve it. Converting MP4 to WebM lets you offer a faster-loading, royalty-free video on your site alongside an MP4 fallback for Safari.

Choose VP9 for the best compression or VP8 for the widest compatibility with older browsers. The audio is encoded to Opus, and the entire conversion runs locally in your browser.

Private by design: your MP4 file is converted on your own device and never uploaded.
WebM already asked for: the AI assistant's request says WebM, so one drop does it. Want a particular resolution, frame rate or bitrate? Just say so.
Batch friendly: the classic converter on this page takes several MP4 files in one go and downloads them as a ZIP.
Free, no watermark: no sign-up, and nothing stamped on the output.

MP4 vs WebM

MP4 (MPEG-4 Part 14): MP4 is the most widely supported video container in the world. It usually carries H.264 or H.265 video with AAC audio, plays on every phone, browser, TV and editing app, and is the safest choice for sharing. It is best for sharing, social media, web playback and mobile devices.

WebM (WebM): WebM is the open, royalty-free container built for the web. It pairs VP8, VP9 or AV1 video with Opus or Vorbis audio and streams natively in Chrome, Firefox, Edge and HTML5 players. It is best for HTML5 video, websites and open-source projects.

In short: keep MP4 when the priority is sharing, social media, web playback and mobile devices, and switch to WebM when the file is headed for HTML5 video, websites and open-source projects. Need a different target? The full Video Converter supports every format listed below.

MP4 to WebM FAQ

Does Safari play WebM?

Safari 14.1 and later on macOS play WebM, but iOS support is limited. Serve WebM first with an MP4 fallback in your video element for full coverage.

VP8 or VP9?

VP9 produces smaller, better-looking files and is supported by every current browser. Use VP8 only if you must support very old Android or browser versions.

Is this MP4 to WebM converter free?

Yes. Converting MP4 to WebM on MediaConverter.io is free, with no watermark and no sign-up. The AI assistant runs on a free daily allowance of assistant credits; the classic converter on this page has no daily limit at all.

Are my MP4 files uploaded to a server?

No. The conversion runs inside your browser using WebCodecs and FFmpeg compiled to WebAssembly, so your .mp4 file is read and converted on your own device and never uploaded, which keeps private recordings private and means there is no waiting in an upload queue. The AI assistant only sees what you type and basic facts about the file: its name, format, duration and size.

Is there a file size limit for MP4 to WebM?

There is no plan or account limit, but the converter loads the whole MP4 file into your browser's memory, so about 2 GB per file is the practical ceiling; larger files may fail to open. Long or high-resolution files also take longer, especially on phones.

Can I choose the WebM settings myself?

Yes. Ask the AI assistant for a resolution, frame rate or bitrate in your request. Audio and subtitle track selection, the codec list and every other setting are in the classic converter, one click away on this page.

Will converting MP4 to WebM reduce quality?

The video is re-encoded into WebM. Keep the source codec, resolution and bitrate (the defaults) and an ordinary 8-bit video is visually the same as your MP4, while a 10-bit, HDR or full-color (4:2:2 or 4:4:4) source can lose some color detail. Lowering the bitrate or resolution is what reduces quality, and you control that trade-off by asking for it (or in the classic converter's settings).

Which browsers support the MP4 to WebM converter?

It is built and tested on current desktop Chrome and Edge, which are also fastest because they expose hardware-accelerated WebCodecs video decoders. Recent Firefox and Safari releases support the same web APIs; if a file fails there, try Chrome or Edge.