WebM to MP4 Converter — Free, No Upload, No Watermark

Convert WebM to MP4 without uploading your video

WebM is what browsers, screen recorders and many web downloads produce, and it is the format that editors, phones and messaging apps most often refuse. Converting to MP4 makes the same video usable everywhere. The picture and sound are re-encoded once, to H.264 and AAC.

Why a WebM will not open

WebM was designed for web pages, and it plays well in browsers. Video editors, many phones, smart TVs and some messaging apps expect MP4 instead and either refuse a WebM or play it without sound. The same applies to the WebM files that browser-based recorders save, which is why converting is such a common step.

Why it is always re-encoded

WebM holds VP8, VP9 or AV1 video with Vorbis or Opus sound, and those are not the codecs that every MP4 player accepts. To make a file that plays everywhere, the converter re-encodes the picture to H.264 and the sound to AAC. That takes longer than a copy, and a smaller video or a lower quality setting makes it faster.

Files from recorders

WebM files recorded straight in a browser often do not store their length, so a player cannot show a progress bar or skip ahead. Converting writes the length in. Recordings from the online screen recorder and the webcam recorder can be converted here, or with the Convert to MP4 button those tools offer.

How this converter works

The page reads your WebM file's header first. If the picture is H.264 and the sound is AAC or MP3, they are copied into the new MP4 without re-encoding, which takes seconds and loses nothing. Anything else is re-encoded to H.264 and AAC at the quality you choose, so the result plays everywhere.

Frequently asked questions

How do I convert WebM to MP4?

Drop your WebM file into the box above, or click to choose it, pick a quality and press Convert to MP4. When it finishes, press Download. The conversion runs in your browser, so the video stays on your device.

Is my video uploaded when I convert it?

No. The conversion runs inside your browser with a WebAssembly build of FFmpeg, and only the engine itself, about 31 MB, is downloaded, once. Your WebM file never leaves your device, and there is no watermark and no account.

Will converting WebM to MP4 reduce the quality?

Often not. If the picture inside the WebM is already H.264 with AAC or MP3 sound, it is copied into the MP4 unchanged. Otherwise it is re-encoded once, to H.264 and AAC, at the quality you choose, and the difference is hard to see at Balanced or High.

What is a WebM file?

WebM is an open, royalty-free format designed for the web. It holds VP8, VP9 or AV1 video with Vorbis or Opus sound, and it plays in all current browsers, but many editors, phones and older Apple software handle it badly or not at all.

What is MP4?

MP4 is the most widely supported video container. It usually holds H.264 (sometimes HEVC) video with AAC sound, and it plays on practically every phone, computer, TV and browser, which makes it the safe default for sharing and uploading.

Why does my WebM video have no sound in my editor?

Many editors cannot read Opus or Vorbis sound inside WebM. Converting to MP4 re-encodes the sound to AAC, which editors read without trouble.

Is a WebM to MP4 conversion slower than other conversions?

It can be, because the picture is always re-encoded rather than copied. Picking a smaller quality setting, or cutting the video shorter first, makes it faster.