WebM to MP4 converter
This makes an MP4 out of the WebM you already have. MP4 is the usual choice for video for the web, social platforms and messaging apps. Your file never leaves your computer.
Need the other direction? Convert MP4 to WebM
How to convert WebM to MP4
- 1 Drop your WebM .webm file onto the page, or click to browse for it.
- 2 Set the quality, or leave the default, which keeps the file small without anything showing.
- 3 Convert. The work happens on your own machine, so how long it takes depends on your computer and the file.
- 4 Download the MP4, or add more files and do the whole set in one go.
Why convert WebM to MP4
- Plays on effectively every device, browser and TV made this century.
- Plays without draining the battery, because devices handle it natively.
- Anything that simply has to play, wherever it is opened.
- WebM: many TVs, editors and older devices will not open it.
WebM compared with MP4
How the two formats differ on the things that decide whether a conversion is worth making.
| Property | WebM | MP4 |
|---|---|---|
| File extension | .webm | .mp4 |
| Transparency | Yes | No |
| Browser support | All current browsers | Every browser |
| Introduced | 2010 | 2001 |
| Developed by | ISO/IEC MPEG |
Quality and what changes
Both formats are lossy, so this is a second generation of compression: the WebM is decoded back to pixels that already carry its artefacts, and MP4 then compresses that. The damage compounds rather than cancelling out, which is why repeated round trips visibly degrade an image. Encode at a higher quality than the source used, and convert once from the best copy you have rather than from an already converted file.
- One MP4 limitation to keep in mind: larger than the newest web formats at the same visual quality.
Questions about WebM to MP4
Will converting WebM to MP4 lose quality?
A little. Both formats are lossy, so the file is decoded and compressed a second time and the two sets of artefacts add up. At a high quality setting the difference is hard to see, but avoid repeated round trips between lossy formats.
Is my WebM file uploaded anywhere?
No. The whole thing runs inside the browser tab you already have open. Your WebM is read straight from your own disk, converted on your machine and handed back as an MP4. Nothing is sent anywhere, nothing is stored and there is no account.
Is there a file size limit?
There is no server-side limit because no server sees the file. The real ceiling is your device memory, since the input and the output both have to fit in the tab. A few hundred megabytes is usually fine on a desktop machine and considerably less on a phone.
Can I convert several WebM files at once?
Yes. Add as many as you like and they are processed one after another, then offered as separate MP4 downloads or as a single ZIP. Speed depends on your own processor rather than on a queue.
Does the converter work offline?
Yes, after the page has loaded once. The engine is cached by the browser, so you can disconnect, reload and keep converting. That falls out of doing the work locally rather than being a separate mode you switch on.