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MP4 to WebM Converter

Going the other way: turn an MP4 into WebM, the open, royalty-free format the web was built around. Developers use WebM for HTML5 background videos and <video> sources because VP9 usually beats H.264 on size at the same quality; some upload pipelines and Linux workflows simply require it. The re-encode runs on your own hardware in the browser — no upload, no watermark, no signup.

  • No upload — files stay on your device
  • Works offline once loaded
  • Free forever, no signup, no watermark
Drop your {{ fromLabel }} file here, or tap to choose Converted to {{ toLabel }} on your device — nothing is uploaded
Reading the file…

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  • File {{ sourceSizeLabel }}
  • Duration {{ durationLabel }}
  • Resolution {{ resolutionLabel }}
  • Video codec {{ info.videoCodec || '—' }}

Instant conversion — the streams are copied, no re-encoding, no quality loss

This file needs a re-encode to become {{ toLabel }}. Your browser's hardware encoder does the work — expect roughly the video's playing time or less.

Heads up: this file is over 500 MB. It will still work — everything streams from disk — but a re-encode can take a while, especially on a phone.

{{ instant ? 'Copying streams into the new container…' : 'Re-encoding with your hardware encoder…' }} {{ progress }}%

Preview
  • Original {{ sourceSizeLabel }}
  • {{ toLabel }} file {{ resultSizeLabel }}

Video stream copied untouched — identical quality to the original.

The audio track used a codec this browser could not convert, so the output is silent.

How to use this tool

  1. Drop your MP4

    The tool probes the codecs first — H.264/AAC MP4s need a re-encode to become WebM, and it tells you so before starting.

  2. Convert to WebM

    Video is re-encoded to VP9 (or VP8) and audio to Opus using the encoders built into your browser. Resolution and frame rate are kept as-is.

  3. Download the .webm

    Drop it into a <video> tag, an upload pipeline, or wherever WebM was demanded — it plays natively in Chrome, Firefox and Edge.

Questions people ask

Why would I convert MP4 to WebM?

Three common reasons: web pages (WebM/VP9 files are typically noticeably smaller than H.264 MP4 at the same quality, which matters for background and hero videos), platforms or pipelines that only accept WebM, and preferring a fully open, royalty-free format.

Which codec does the output use — VP8 or VP9?

The tool asks your browser for its best available WebM encoder: VP9 where supported (smaller files, better quality), falling back to VP8. Audio becomes Opus, WebM's native audio codec.

Will the WebM play in Safari?

Modern Safari (macOS 11.3+/recent iOS) plays most WebM, but support arrived late and older Apple devices skip it entirely. For a website, the standard practice is to list the WebM source first and keep an MP4 fallback source after it in the <video> tag.

Does the conversion reduce quality?

It is a real re-encode, so a small generational loss is unavoidable — but resolution and frame rate are preserved and the encoder targets quality parity, not compression. If your goal is a smaller file rather than a different format, a video compressor is the better tool.

Is my video uploaded anywhere?

No — the whole conversion runs inside your browser through WebCodecs. You can watch your network tab stay silent while it works.

Which browsers can convert to WebM?

Chrome and Edge can encode VP8/VP9 on effectively all machines. Firefox and Safari often cannot — the tool feature-detects and says so up front rather than failing midway.

Related tools

Free because it costs us nothing to run: your browser does the work, not our servers. Made by Dynamb Technologies — we build software for businesses.