Convert WebM to MP4 online
Convert a WebM video (typical of browsers and web recordings) to MP4, the most compatible format, right in your browser and without uploading it to any server.
Convert WebM to MP4
Your file is processed right in this browser: it never gets uploaded to any server.
Why use PullVid for WebM → MP4?
Conversion details
How do you convert a WebM to MP4?
Choose the WebM file you want to convert to MP4.
Hit 'Convert'. Unlike MKV or MOV, WebM gets fully re-encoded, so it can take longer: wait for the progress bar to reach 100%.
Download the resulting MP4; it saves straight to your device.
If you have a video in WebM format and need to share it on WhatsApp, upload it to a social network, or open it in an editing program that doesn't handle it well, this converter turns it into MP4 right in your browser, without uploading the file to any server.
What's converting a WebM to MP4 good for?
WebM works great inside the browser — it's lightweight and Chrome, Firefox or Edge play it without issue — but outside of that, compatibility drops off fast: WhatsApp, the iPhone's Photos app and many video editors either prefer or flat-out require MP4. Converting it widens where you can use that video without changing its content.
How it works: this one really does re-encode
Unlike the MKV to MP4 or MOV to MP4 conversions, which only swap the container (instant remux), this time the video is genuinely re-encoded with ffmpeg compiled to WebAssembly: the video becomes H.264 (libx264) and the audio becomes AAC. It's a heavier process, so it takes time proportional to the video's length and your device's power, instead of the few seconds a remux takes.
Steps to convert your WebM to MP4
- Choose the WebM file from your device ('Choose file' button).
- Hit 'Convert'. The first time, your browser downloads the conversion engine (a few MB); after that, it's faster.
- Wait for the progress bar to reach 100% — this can take longer than other conversions because the whole video gets re-encoded.
- Download the resulting MP4 with the 'Download result' button.
Honest limits worth knowing
Since it genuinely re-encodes rather than just copying data, this conversion uses more time and memory than a remux: long videos (several minutes) or very heavy ones can take a good few minutes and push your browser's memory hard, especially on phones with limited RAM. This converter processes one thread at a time, so for long videos you'll do better on a computer than on a phone.
Other related conversions
If your video is already in MKV or MOV instead of WebM, those conversions are much faster since they only swap the container: try MKV to MP4 or MOV to MP4. If all you want is the audio, convert to MP4 first and then use MP4 to MP3. If you don't have the video yet, use our YouTube video downloader.
Frequently asked questions about WebM → MP4
Why does this take longer than other conversions to MP4?
Because WebM uses video (VP8/VP9) and audio (Opus/Vorbis) codecs that MP4 doesn't natively support. Unlike MKV or MOV, which only swap the container, here the entire video has to be re-encoded to H.264 and the audio to AAC, which uses more time and device power.
Is quality loss noticeable when re-encoding?
We use a balanced setting (x264's 'veryfast' preset) designed to keep quality loss minimal and barely noticeable. Even so, since this is a genuine re-encode — not a copy — there's always some additional compression, the same as opening and re-exporting any video with another program.
Where do WebM files usually come from?
It's the typical format for videos recorded from the browser (screen recordings, WebRTC video calls), some videos embedded on web pages, and certain very high-quality YouTube downloads that only exist in WebM (VP9 codec).
Is there a limit on the video's length?
We don't set an artificial limit, but since it's genuinely re-encoded (not just copied), long or heavy videos can take several minutes and use quite a bit of memory, especially on phones. For videos longer than a few minutes, you'll have better luck on a computer.
I don't have the WebM file yet — can I download it here?
This converter works with a file you already have saved on your device. If instead you want to download a video from YouTube or another site, use our YouTube video downloader, which delivers directly in MP4.