Convert WEBM to MP4
Runs in your browser. Your files never leave your device.
How we keep your files private
How to use Convert WEBM to MP4
- Choose or drop your WEBM file.
- Wait while your browser converts it to MP4 (the first run downloads the converter once).
- Download the MP4 file.
Common uses
- Playing videos on phones, TVs and websites.
- Uploading videos to platforms that prefer MP4.
- Making files compatible with editors.
About this tool
WEBM is an open video format designed for the web. MP4 is the most widely supported video format, usually H.264 video with AAC audio.
Conversion runs on your device with FFmpeg compiled to WebAssembly, so your file is never uploaded. The first conversion downloads the engine (about 30 MB), which your browser then caches. Large files need a lot of memory, so use a desktop browser for videos over a few hundred megabytes.
Next steps
Frequently asked questions
Is my file uploaded?
No. The conversion runs in your browser with FFmpeg compiled to WebAssembly.
Why is the first conversion slow?
The converter engine (about 30 MB) downloads once and is cached. Conversions then run on your device, so large files take time.
Will converting WEBM to MP4 reduce quality?
Lossy formats lose a little quality each time they are re-encoded. Lossless targets such as WAV or FLAC keep what the source has.
What is the maximum file size?
There is no fixed limit, but browser memory is: files of a few hundred megabytes can work on a desktop, much less on phones.
Which codecs are used?
H.264 video and AAC audio, the most widely supported combination.
Are my files uploaded to a server?
No. Everything runs inside your browser on your own device, so your files and text are never sent anywhere.
Is it really free?
Yes. There is no sign-up, no watermark and no limit on how often you use it.
Does it work on my phone?
Yes. It works in any modern browser on phones, tablets and computers. Very large files may be slow on older phones.