Convert WebM to MP4 Online — Free & Instant
Turn WebM screen recordings into universally compatible MP4 files.
How It Works
- 1Upload your file by dragging it into the drop zone or clicking to browse.
- 2Adjust the quality slider to balance file size and visual fidelity (optional).
- 3Click Download to save your converted file.
About WebM to MP4
WebM is the default format for browser screen recordings, but many devices, social media platforms, and video editors prefer MP4. This tool transcodes your WebM file to H.264/AAC MP4 — the most widely supported video format. Uses FFmpeg.wasm running entirely in your browser via WebAssembly. No files are uploaded, and processing happens on your device.
Frequently Asked Questions
Why convert WebM to MP4?
WebM is great for web playback but has limited support on iOS, some Android apps, and many video editors. MP4 (H.264/AAC) is the most universally compatible video format.
Is my file uploaded to a server?
No. Transmute processes everything locally in your browser using JavaScript and the Canvas API. Your files never leave your device — there is no server, no upload, no cloud processing.
Will the quality change?
There will be minimal quality difference. The tool uses CRF 23 which provides a good balance between file size and visual quality. The output may be slightly larger or smaller depending on the content.
How long does conversion take?
It depends on the video length and your device. A 1-minute WebM typically converts in 30-60 seconds on a modern computer. The FFmpeg.wasm engine runs in your browser using WebAssembly.
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