WebM to MP4 Converter
Convert WebM to MP4 in your browser. Screen recordings, browser captures and clips saved from the web are re-encoded from VP9 or VP8 to H.264 with AAC sound, so they play on iPhone, Windows, TVs and in every editor.
- Free
- No upload
- No watermark
Files
Settings for all files
Options · Same quality · Original size · Sound on
More options
GIFs can be up to 60 s long (30 s on phones). Use Trim (⋯ on a file) to pick a part.
Same copies AAC sound without re-encoding when the file already has it.
16-bit PCM, the format CDs and every audio editor use.
Add files to see what will happen to each one.
Add files to convert
Runs in your browser. Engine: mp4box.js (BSD-3-Clause), mp4-muxer and webm-muxer (MIT), gifenc (MIT), LAME via lamejs (LGPL-3.0, GPL-3.0) – licenses.
What works in your browser
Everything runs on your device, so what you can create depends on the browser. The last column is checked live in the browser you are using now and always wins over the table.
| Output | Chrome / Edge | Chrome Android | Firefox 130+ | Safari 16.4–18 | Safari 26+ | This browser |
|---|---|---|---|---|---|---|
| MP4 (instant copy) | Yes | Yes | Yes | Yes | Yes | Yes |
| MP4 (re-encode, H.264) | Yes | Yes | Yes, sound as Opus | Yes, AAC sound copied only | Yes | – |
| MOV | Yes | Yes | Copies only | Yes, AAC sound copied only | Yes | – |
| WebM (VP9 + Opus) | Yes | Yes (slow) | Yes | Checked live | Checked live | – |
| GIF | Yes | Yes | Yes | Yes | Yes | – |
| MP3 | Yes | Yes | Yes | Yes, long files limited | Yes | – |
| M4A | Yes | Varies by device | Copies only | Copies only | Yes | – |
| WAV | Yes | Yes | Yes | Yes, long files limited | Yes | – |
| Opus | Yes | Yes | Yes | Copies only | Checked live | – |
Instant copies work in every browser. Without WebCodecs (older browsers) re-encoding is not available, but MP3 and WAV files can still be made.
How to convert WebM to MP4
- Pick the WebM files, for example a screen recording from your Downloads folder.
- MP4 is selected for you. Choose Same quality, Balanced or Smaller file, and a lower resolution if the video is very large.
- Press Convert. Re-encoding runs faster than real time on most computers; the row shows progress and the time left.
- Download the MP4 and share it anywhere – it now opens on iPhone, in WhatsApp, PowerPoint and video editors.
Made for screen recordings
Sharp text
Small text and interface edges stay readable – the usual weak spot when recordings are compressed.
Variable frame rate kept
Frames are encoded at their original times, so a recording that paused or slowed down stays in sync with its sound.
Resize while converting
Pick 1080p or 720p to make a 4K capture easier to share; a video is never enlarged beyond its own size.
Frequently asked questions
Is WebM to MP4 really free, without upload?
Yes. There is no sign-up, no limit on the number of files and no watermark, and the WebM is converted by your own browser. Screen recordings often show private things, and here they never leave your device.
Will I lose quality going from WebM to MP4?
WebM to MP4 needs a re-encode, but at "Same quality" the H.264 bitrate is set high enough that the difference is not visible in normal viewing. Choose Smaller file only if size matters more than detail.
Why does my WebM screen recording show no duration?
Browsers record WebM on the fly and often never write the total length into the file. Zebra Convert reads the end of the file to work out the length and writes a correct duration into the MP4, so players can show it and seek properly.
How long does WebM to MP4 take?
On a recent computer a 10-minute 1080p recording takes about five minutes or less; on a phone, about as long as the video. The estimate appears next to each file before you start, and you can cancel at any time.
Which browsers can convert WebM to MP4?
Chrome and Edge do it fully, including AAC sound. Firefox and Chrome on Linux create H.264 but no AAC, so the sound becomes Opus inside the MP4 and the row tells you before you start. Safari support depends on the version and is checked live.
What happens to quality
WebM files hold VP8, VP9 or AV1 video with Opus or Vorbis sound – formats designed for browsers, but not accepted by many phones, TVs and editing apps. To make an MP4 that plays everywhere, Zebra Convert decodes each frame and encodes it again as H.264, and converts the sound to AAC. With "Same quality" the bitrate is chosen from the original, so the result looks the same; "Balanced" and "Smaller file" trade a little detail for a smaller download.
Recordings from Chrome, OBS or a screen recorder often have no length stored in the file and change frame rate while you work. The converter works out the length from the file itself and keeps the original timing of every frame, so the MP4 stays in sync with the sound. If this browser cannot create H.264, the VP9 video can still be copied into MP4 for browsers and VLC.