Convert WebM to MP4 Online

Upload a WebM file and convert it to universally compatible MP4. No software to install, works directly in your browser.

How it works

  1. Upload your WebM video. Drag your WebM file into DomeScribe. Files using VP8, VP9, or AV1 video codecs and Opus or Vorbis audio are all accepted.
  2. Inspect codec and stream info. DomeScribe analyzes the WebM container and shows the exact video and audio codecs, resolution, and duration so you know what you are working with.
  3. Configure MP4 output parameters. Pick your preferred video codec (H.264 for broad device support or H.265 for efficiency) and audio codec (AAC is recommended). Adjust resolution and bitrate as needed.
  4. Convert and save the MP4 file. Click Convert to transcode your WebM into MP4. The resulting file is compatible with virtually every media player, social platform, and mobile device.

Converter at a glance

Video formats
MP4, WebM, MOV, AVI, MKV
Audio formats
MP3, WAV, FLAC, M4A, OGG, AAC
Privacy
Runs 100% in your browser (WebAssembly) — your file is never uploaded to a server
Speed
No upload or download wait — conversion starts instantly, even for large files
Watermark
None, ever
Free tier
10 conversions per month

Frequently asked questions

Why won't my WebM file play on my phone or TV?

WebM uses VP8, VP9, or AV1 codecs that many hardware devices do not decode natively. iPhones, most smart TVs, and older Android devices lack built-in WebM support. Converting to MP4 with H.264 encoding in DomeScribe solves this compatibility issue instantly.

Is WebM to MP4 conversion lossy?

Yes, since WebM and MP4 typically use different video codecs, a full transcode is required. However, DomeScribe uses high-quality encoding defaults that make the visual difference negligible in nearly all practical scenarios.

I downloaded a WebM from a website — can I convert it?

Yes. WebM is the default format many websites and browsers use for embedded video. Simply upload the downloaded WebM file and DomeScribe will transcode it to a universally playable MP4.

Will the file size change when going from WebM to MP4?

It depends on the source codec and the settings you choose in DomeScribe. VP9 WebM files are already quite efficient, so the MP4 may be similar in size or slightly larger. AV1 WebM files may produce a somewhat larger MP4 since H.264 is less efficient than AV1.

Does the conversion preserve the original resolution and frame rate?

By default, DomeScribe matches the source resolution and frame rate exactly. You can optionally downscale — for example, from 4K to 1080p — to reduce file size if the full resolution is not needed.

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