WebM to MP4 Converter
Upload a WebM file and convert it to MP4 format directly in your browser — your video never leaves your device.
Select WebM File
All processing runs locally in your browser via FFmpeg.wasm.
No file is ever uploaded. FFmpeg (~30 MB) is fetched once from a CDN and cached for future use.
Command-Line Alternative (FFmpeg)
For large files or batch conversion, use FFmpeg on the desktop for much faster processing.
# High quality (CRF 20)
ffmpeg -i input.webm -c:v libx264 -crf 20 -c:a aac -b:a 192k output.mp4
# Batch convert all WebM in a folder
for f in *.webm; do ffmpeg -i "$f" -c:v libx264 -crf 20 -c:a aac "${f%.webm}.mp4"; done
ffmpeg -i input.webm -c:v libx264 -crf 20 -c:a aac -b:a 192k output.mp4
# Batch convert all WebM in a folder
for f in *.webm; do ffmpeg -i "$f" -c:v libx264 -crf 20 -c:a aac "${f%.webm}.mp4"; done
Choose a WebM file and click Convert to get started.
Output will be H.264 MP4 — compatible with all devices.
Initializing FFmpeg...
0%
Your file is being transcoded locally. This may take a minute for longer videos.
What is happening?
- WebM container is decoded by FFmpeg.wasm
- Video is re-encoded to H.264 (libx264)
- Audio is re-encoded to AAC for maximum compatibility
An error occurred.
Try a different file or refresh the page and try again.
WebM vs. MP4 — Compatibility Overview
| Platform / Device | WebM | MP4 (H.264) |
|---|---|---|
| Chrome / Firefox / Edge | Yes | Yes |
| Safari / iPhone / iPad | No | Yes |
| Android devices | Yes | Yes |
| Smart TVs / Chromecast | Limited | Yes |
| YouTube / Vimeo upload | Yes | Yes |
| Twitter / Instagram | No | Yes |
| Premiere / Final Cut | Limited | Yes |
| WhatsApp / iMessage | No | Yes |
Summary
Upload a WebM file and convert it to MP4 format directly in your browser — your video never leaves your device.
How it works
- Click "Choose WebM File" and select any .webm video from your device.
- FFmpeg.wasm loads in your browser (one-time download, approximately 30 MB).
- Choose an output quality preset: Fast (lower file size) or High Quality (larger file).
- Click "Convert to MP4" to start transcoding with H.264 video and AAC audio codecs.
- A progress bar shows the conversion status in real time.
- When done, click "Download MP4" to save the converted file.
Use cases
- Share WebM screen recordings on platforms that require MP4, such as Twitter or Instagram.
- Make WebM clips playable on iPhones, Apple TV, and other Apple devices.
- Import WebM footage into video editors like Premiere Pro, Final Cut Pro, or DaVinci Resolve.
- Upload WebM recordings to video hosting platforms that prefer H.264 MP4.
- Convert browser-captured WebM videos for offline or archival storage.
- Process sensitive footage privately — no file ever leaves your device.
Frequently Asked Questions
Last updated: 2026-06-11 ·
Reviewed by Nham Vu