Convert WebM to MP4
Turn WebM files from browser screen recorders and some meeting tools into MP4 that opens on iPhone and in video editors.
Settings
How to use
- 1
Add videos
Drop MP4, MOV, WebM, MKV and similar files. Several videos can be converted in turn with the same settings.
- 2
Choose the output format
MP4 (H.264), WebM (VP9), MOV or MKV. When the codec already matches, the stream is copied instead of re-encoded, which is very fast.
- 3
Convert and save
Save once the progress bar reaches 100%. Long videos take a while; keep the tab open.
Why WebM will not open
WebM is Google's web-oriented video format using VP8 / VP9 video and Opus audio. Browsers play it, but the iPhone Photos app, most video editors and TVs do not.
MP4 (H.264 + AAC) plays on virtually every device and program. VP9 to H.264 requires re-encoding, so the time taken scales with the video length.
Frequently asked questions
Is quality lost?
It is re-encoded, so it changes slightly according to the Quality setting. At "High" or above the difference is negligible.
The output has no audio
The screen recording may have been made without microphone or system audio. If the WebM has an audio track it is converted to AAC and included.
My WebM shows a length of 0 or invalid
WebM produced by the browser MediaRecorder API often lacks duration metadata. This tool reads the whole file to determine the length, so it converts fine.
It does not work in Firefox
Firefox supports WebCodecs from version 130 on desktop. On older versions or Android, use Chrome or Edge.
Help us improve the service
If a conversion fails, sending us the circumstances helps us track down the cause. Knowing which devices and formats fail most often, and how long processing takes, lets us revise the supported formats and fix the bugs behind them. If you don't mind, leaving this on is a real help.
What is sent
The tool you used and the settings you chose (output format, quality, etc.), your device specs (GPU, memory, core count), the input format with a rough size, how many files succeeded or failed and how long it took, and the error type and details when something fails.
What is never sent
The files themselves, file names, text, subtitles or prompts you add to a video, and IP addresses. The data goes only to this site's own server, never to a third-party service.