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WebM to MP4 Converter

Turn WebM videos into MP4 files that play everywhere. WebM recordings from browsers, screen recorders and web downloads use VP8 or VP9 video, which some phones, editors and TVs cannot open; this converter re-encodes them to H.264.

  • Files stay on your device
  • No sign-up
  • Free to use

How to use WebM to MP4

  1. Drop a WebM file onto the upload area.
  2. Choose the quality: High, Balanced or Smaller file.
  3. Optionally limit the resolution to make the file smaller.
  4. Select Convert to MP4 and download the H.264 MP4.

WebM to MP4 features

VP8 and VP9 to H.264

Converts both common WebM video codecs to the most compatible format.

Opus and Vorbis to AAC

Audio is converted to AAC for MP4 players.

Fixes browser recordings

Handles WebM files recorded with MediaRecorder, which sometimes lack duration information.

Quality presets

Balance file size and quality with three simple levels.

Optional downscaling

Limit large recordings to 1080p, 720p or 480p.

On-device

No uploads; FFmpeg runs in your browser.

When to use WebM to MP4

  • Playing browser screen recordings on an iPhone or in PowerPoint.
  • Editing WebM clips in software that only accepts MP4.
  • Sharing web-recorded meetings or demos as MP4.
  • Converting downloaded WebM videos for TVs and media players.
  • Uploading WebM recordings to platforms that require MP4.

WebM to MP4 FAQ

Why can’t I just rename .webm to .mp4?

The extension only names the container. The video inside a WebM file is VP8 or VP9, which many MP4 players do not support. It must be re-encoded to H.264.

Why is there no fast option for WebM?

Although MP4 can technically contain VP9, many devices fail to play it that way. Re-encoding to H.264 is the only reliable route, so this converter always does that.

Will the MP4 be larger than the WebM?

Often slightly, because VP9 is more efficient than H.264. Choose Smaller file or a lower resolution if size matters.

My recording shows no duration or cannot be seeked. Will it work?

Yes. Files recorded in browsers often lack an index. Converting rebuilds a proper MP4 with duration and fast seeking.

Is the conversion done online?

It is done on your own device by FFmpeg compiled to WebAssembly. The video is never uploaded.

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WebM, VP9 and compatibility

WebM was introduced by Google in 2010 as an open, royalty-free video format for the web. It combines the Matroska container with VP8 or VP9 video and Vorbis or Opus audio. Browsers adopted it widely, and it remains the default output of browser-based recording through the MediaRecorder API, used by many screen recorders and meeting tools.

Outside browsers the picture is less consistent. Older iPhones, many TVs, some Windows apps and most video editors historically lacked VP9 decoding, and even where it works it may drain batteries faster without hardware support. H.264, by contrast, has dedicated decoding hardware in practically every device, which is why it remains the safe choice for sharing.

Browser recordings have another quirk: because they are written while recording, the file often lacks the index that tells players its total length. Players then show no duration and cannot jump ahead. Converting produces a complete MP4 with a proper index at the start, making seeking instant.

If you need the opposite, such as smaller files for your own website, the MP4 to WebM converter produces VP9 WebM files that browsers play efficiently.

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