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Convert WebM to MP4 Online

xFormat converts WebM videos, such as screen recordings and web downloads, into MP4 (H.264/AAC) inside your browser, so they play almost anywhere and the file never leaves your device.

Runs in your browser — files never leave your device.

How it works

Browser-based screen recorders and many downloaded clips come out as WebM, which iMovie, some editors and older devices will not open. Convert it to MP4 here. The video is re-encoded locally, so expect it to take a little longer than a simple file swap.

  1. 1

    Select your WebM file.

  2. 2

    Keep MP4 as the output format.

  3. 3

    Click Convert and wait for the progress bar to finish, then save.

Why WebM to MP4 usually needs a re-encode

WebM contains VP8 or VP9 video with Vorbis or Opus audio. MP4 players overwhelmingly expect H.264 video with AAC audio. Since those codecs are different, the container cannot simply be swapped: the video has to be decoded and compressed again as H.264, and the audio as AAC.

That costs time and a small amount of quality, but it is what makes the file play in QuickTime, on iPhones, in video editors and in apps that reject WebM.

Getting the best result from a screen recording

Screen recordings often have a variable frame rate, because the browser only records frames when something on screen changes. If your editor shows odd timing or audio drift after import, converting to MP4 first generally helps, since most editors handle H.264 more predictably.

Your browser's hardware-accelerated encoders are used where your device supports them, which can speed up the encoding noticeably. If the browser cannot handle the file, compatibility mode (a one-time download of about 31 MB) takes over.

Limits

Around 500 MB on desktop and 200 MB on phones is the practical ceiling. Long, high-resolution recordings are better converted on a computer.

Frequently asked questions

How do I convert a WebM screen recording to MP4?

Choose the WebM file here, keep MP4 selected and click Convert. It is re-encoded in your browser to H.264 video and AAC audio.

Why is WebM to MP4 slower than MOV to MP4?

Because the codecs differ, the video must be fully re-encoded rather than just repackaged. Hardware acceleration helps where available.

Will the converted MP4 play on iPhone and in iMovie?

H.264/AAC MP4 files are the most widely supported combination, so they generally open on iPhone, Mac, Windows, Android and in common editors.

Is the WebM file uploaded?

No. Everything is processed locally and the file never leaves your device.

Is there a watermark or sign-up?

No. It is free and works without an account or watermark.

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