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Home » Video Tools » WebM to MP4 Converter

WebM to MP4 Converter

Convert WebM videos, such as screen recordings from OBS or Chrome and clips saved from websites, to MP4 (H.264 + AAC), which plays on iPhone, Windows, WhatsApp and every video editor.

🔒 Your video is processed locally in your browser. Your file is never uploaded.

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You may also need

  • MP4 to WebM Converter — Convert MP4 videos to WebM (VP8/Opus) for websites and HTML5 video, right in your browser.
  • MOV to MP4 Converter — Convert iPhone and QuickTime MOV videos to MP4 — usually in seconds, without losing quality.
  • Video Resizer — Change video resolution or aspect ratio — 1080p, 720p, square 1:1 or vertical 9:16 for Reels, TikTok and Shorts.
  • Video to MP3 (Extract Audio) — Extract the sound from a video as MP3, M4A or WAV — in your browser, without uploading the video.

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How to use it

  1. Choose a video (or drop it on the box). The format and length are detected automatically.
  2. Pick the output format, quality and resolution.
  3. Click "Convert", wait for the progress bar and download the result.

Why convert WebM to MP4?

WebM is great in browsers, but many apps still can't open it: older iPhones, WhatsApp, PowerPoint, Premiere and many TVs expect MP4 with H.264. WebM files use VP8, VP9 or AV1 video, which can't simply be copied into an MP4, so this converter re-encodes the video to H.264 in your browser. "High" quality keeps screen-recording text sharp.

Screen recordings are often long. Cut out the part you need first with the Video Trimmer; it keeps the WebM format and finishes instantly. Then convert only that clip.

Frequently Asked Questions (FAQ)

Q: Is my file uploaded to a server?
A: No. The tool runs FFmpeg compiled to WebAssembly inside your browser tab. Your file is read directly from your device and the result is created locally. Only the video engine itself (open-source ffmpeg.wasm, about 10 MB compressed) is downloaded the first time, from a public CDN; after that it is cached.
Q: How big can the file be?
A: Up to about 500 MB works well on a computer and about 150 MB on a phone. Larger files may still work but can be slow or run out of browser memory. Trimming the clip or lowering the resolution first helps.
Q: Why is it slower than a desktop app?
A: The browser version of FFmpeg runs on a single CPU core and without hardware acceleration. A 1-minute 1080p re-encode typically takes 1–3 minutes. When possible the tools copy the streams without re-encoding, which takes only seconds.
Q: My WebM from a screen recorder shows a wrong or unknown duration. Is that a problem?
A: No. Browser recorders often don't write the duration into the file. The conversion still works, although the progress bar may be less precise, and the MP4 you get has a correct duration.