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Convert WebM to MP4

Turn your WebM files into MP4 — free, fast and right in your browser.

Runs locally — nothing is uploaded

Drop WebM files here — or click to browse

Files are converted in your browser and never uploaded.

Related conversions

MP4MP3MOVMP4MKVMP4GIFMP4

This tool converts WebM files to MP4 right in your browser. Drop the file, wait a moment for the assessment, convert — the video is processed on your device and never uploaded anywhere. Wherever possible the picture data is repackaged unchanged, which takes seconds and costs no quality.

What is WebM?

WebM is the open, royalty-free web video format Google introduced in May 2010. Technically it is a restricted subset of the Matroska container, limited to the codecs VP8, VP9 and AV1 for pictures and Vorbis or Opus for sound. Browsers, screen recorders such as OBS and every MediaRecorder capture in the browser produce it. The catch: those very codecs are what many video editors, TVs, projectors and older phones do not accept — which is why a WebM often has to become an MP4 before anyone else can use it.

What is MP4?

MP4 (ISO/IEC 14496-14) is the everyday video container: H.264 or HEVC pictures plus an AAC audio track, produced by every phone camera, screen recorder and streaming platform. Container and codec are two different things — an .mp4 file says how the data is packaged, not how it was compressed. That distinction is what makes fast conversion possible: if the pictures inside are already H.264 or HEVC, they can simply be repackaged instead of re-encoded. A typical consumer clip carries its sound at 128 to 192 kbit/s AAC.

Why convert WebM to MP4?

WebM shows up wherever the browser records: screen captures, web meetings, voice and video messages, downloads from video platforms. But the moment the file has to go into an editor, onto a TV, into PowerPoint or onto an older phone, MP4 is what is wanted — WebM is often not even offered there.

Does WebM have to be re-encoded?

Usually yes — and that is the honest difference from MOV or MKV. WebM is defined as a subset of Matroska and only allows VP8, VP9 or AV1 for the picture and Vorbis or Opus for the sound (Google, since May 2010). Those codecs are not what an MP4 player expects. So the picture is decoded frame by frame and re-encoded as H.264: expect roughly the runtime of the video as waiting time, less on a fast machine.

What are the limits?

Re-encoding means a second lossy stage. The result can never be sharper than the WebM, though at the high bitrate used here the difference is hard to see. Two more limits: the conversion needs an H.264 encoder in the browser (recent Chrome, Edge, Firefox and Safari have one, very old devices do not), and transparency from VP9 is lost — MP4 video has no alpha channel.

How to convert

1. Drop your WebM file(s) into the area or click to browse. 2. The tool reads the header and tells you whether it will repackage or re-encode, and roughly how long that takes. 3. Click Convert — progress is shown per file and you can cancel at any time. 4. Download the MP4; multiple files come as a ZIP.

Frequently asked questions

Is converting WebM to MP4 free?

Yes, completely free and without signup. There are no watermarks and no file-size limits beyond what your browser can handle.

Are my files uploaded?

No. The conversion runs entirely in your browser — your WebM file never leaves your device and is not sent to any server.

Do I lose quality converting WebM to MP4?

Usually not. If the WebM already holds H.264 or HEVC with AAC or MP3 sound, the picture data is copied into the MP4 container unchanged — bit for bit the same image, just packaged differently, and done in seconds. Only when the codecs do not fit MP4 (VP9 or AV1, for example) is it re-encoded, which costs a little quality once. The tool shows you which path applies to your file before you start.

Can I convert several files at once?

Yes. Just drop multiple files into the area — they are converted together and you can download them as a ZIP.

How big and how long may the video be?

Up to 2 GB in size. When the file is only repackaged, up to two hours of runtime works — that is fast and needs little memory. When it has to be re-encoded, the limit is 30 minutes, because every frame goes through the encoder individually and the tab has to stay open. Which case applies to your file is shown before you start.

What happens to extra audio and subtitle tracks?

One video and one audio track are carried over — that is what an MP4 transports reliably everywhere. Additional language versions, embedded subtitles and chapter marks stay behind. If you need them, keep the original file as well.

Why does it take seconds for some files and minutes for others?

Because there are two paths. If the codecs fit into an MP4 container, the finished data packets are merely rearranged — pure copying, done in seconds. If they do not, every frame has to be decoded and encoded again, and then the wait is roughly in the order of the video length. The work is done by your device’s encoder, not by a server.