MP4 to MP3 — Free & Private
Extract audio from any video file directly in your browser. No upload, no account — powered by WebAssembly.
Drag & drop files here, or click to browse
Files are processed entirely on your device and are never uploaded to any server.
Frequently Asked Questions about MP4 to MP3 conversion
How does MP4 to MP3 conversion work in the browser?
SwiftConvert uses FFmpeg compiled to WebAssembly (WASM), which runs directly in your browser. It processes the video file locally on your device and extracts the audio stream as an MP3 — no server involved.
What video formats does this tool support?
You can extract audio from MP4, MOV, and WebM video files. The output is high-quality MP3 compatible with all music players and devices.
Will the audio quality be good?
Yes. The tool extracts the original audio stream from the video at the highest quality (variable bitrate mode), matching the source audio quality.
Why is the conversion taking a long time?
Video processing via WebAssembly is computationally intensive. Large files (100MB+) may take a few minutes. The first conversion also has a slight delay while FFmpeg WASM loads — subsequent conversions in the same session are faster.
Is there a file size limit for the video?
Free users can convert videos up to 500MB. Note: very large files may be slow due to browser memory constraints.