Convert WebM to MP4 Online (Free, No Upload)

Drop a WebM file and get an MP4 back. The conversion runs right in your browser, so your video never leaves your device. Completely free, no account required.

Try it in your browser

Loading FFmpeg engine... (~31 MB)

How to webm to mp4 online online

1Drop your WebM file into the tool above, or click to browse your files.
2Leave the default settings for a good balance of quality and file size, or pick a preset if you need something specific.
3Click convert and download your MP4 file when it's ready.

About MP4 format

WebM is an open video format created by Google, built on the VP8 and VP9 codecs. It's common in screen recordings, browser-based captures, and videos downloaded from the web. The format works well for streaming on websites, but outside of a browser it can be a pain. Most video editors, social media platforms, and Apple devices don't handle WebM files.

MP4, on the other hand, is the closest thing to a universal video format. It uses H.264 encoding, which plays on basically every device and app made in the last 15 years. When you convert WebM to MP4, the video gets re-encoded from VP8/VP9 into H.264 and wrapped in an MP4 container. The file size stays roughly the same, and at default quality settings the visual difference is minimal.

Use the API

curl -X POST https://renderio.dev/api/v1/run-ffmpeg-command \
  -H "X-API-KEY: ffsk_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
  "ffmpeg_command": "-i {{in_video}} -c:v libx264 -crf 23 -c:a aac -movflags +faststart {{out_video}}",
  "input_files": {
    "in_video": "https://example.com/input.webm"
  },
  "output_files": {
    "out_video": "output.mp4"
  }
}'

Need an API key? Get your free API key to start processing files programmatically.

Common Variations

High quality preserve

-i input.webm -c:v libx264 -crf 18 -preset slow -c:a aac -b:a 192k output.mp4

Fast encode for previews

-i input.webm -c:v libx264 -preset ultrafast -crf 28 -c:a aac output.mp4

Scale to 1080p max

-i input.webm -vf "scale=min(1920\,iw):-2" -c:v libx264 -crf 23 -c:a aac output.mp4

Strip audio (video only)

-i input.webm -an -c:v libx264 -crf 23 -movflags +faststart output.mp4

Frequently Asked Questions

Is this WebM to MP4 converter really free?+

Yes, 100% free. There's no account to create, no watermark, and no usage cap. You can convert as many files as you want.

Are my files safe? Where do my videos go?+

Your files stay on your device the entire time. Nothing gets uploaded to a server. The conversion happens locally in your browser, so nobody else can access your video.

What's the maximum file size I can convert?+

There's no file size limit on our end. Since the conversion runs on your own device, it depends on your available memory. Most computers handle files up to a few GB without issues.

Why can't I play WebM files on my iPhone?+

Apple's Safari and iOS don't support WebM playback natively. Converting to MP4 (H.264) gives you a file that plays on every Apple device, plus Android, Windows, and pretty much anything else.

Does converting WebM to MP4 lose quality?+

There is some quality loss because the video gets re-encoded from VP8/VP9 to H.264. At our default settings (CRF 23), the difference is hard to spot. If you need higher quality, use the 'High quality preserve' preset.

Does this work on iPhone and Android?+

Yes. It runs in Chrome, Firefox, Safari, and Edge on both desktop and mobile. Larger files may be slower on phones since they have less processing power.

What is a WebM file and why do I have one?+

WebM is a video format developed by Google. You probably got one from a screen recording, a download from a website, or a browser-based video capture. It works well on the web but many apps and devices can't open it, which is why converting to MP4 is useful.

Privacy

Your files never leave your device. The entire conversion runs locally in your browser. Nothing is uploaded to any server, nothing is stored, and we don't track what you convert.

Related Operations

Need to process at scale?

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