Free Online Stereo Widener
Make stereo sound wider - or collapse it to mono.
Drag & drop your audio file here
or
Max file size: 100 MB · MP3, WAV, FLAC, OGG
Original
beats per minute
musical key
100% is the original. Below 100% narrows the image (0% is mono); above 100% pushes the sides wider.
Processing…
Result
How it works
The Stereo Widener reshapes the stereo image using mid/side processing - the same technique mastering engineers use. The "mid" signal (everything panned center: usually vocals, kick and bass) is left alone while the "side" signal (the stereo difference) is scaled: boost it for a wider, more immersive sound, or cut it to narrow an overly wide mix down to focused mono.
One slider covers the whole range: 0% collapses to dual mono (guaranteed mono-compatible, great for club systems and phone speakers), 100% is your original untouched, and up to 200% pushes the sides dramatically outward for headphone listening.
This is a buffer (offline) tool: the whole file is rendered with your width setting and returned as a downloadable file. Everything runs client-side in your browser, so your files never leave your device and nothing is uploaded anywhere.
Frequently asked questions
How does stereo widening work?
It uses mid/side processing: the "mid" (what is identical in both channels) stays fixed while the "side" (the difference between channels) is boosted or cut. Boosting the side makes the stereo image feel wider; cutting it narrows the image toward mono.
Can widening damage my mix?
Extreme widening (near 200%) can make the center (vocals, kick, bass) feel hollow and can cause phase issues on mono playback. Moderate settings (120-150%) are safe on most material - and 0% is always perfectly mono-compatible.
What happens with a mono file?
Nothing - a mono file has no side signal, so it passes through unchanged at any width setting.
Is there a file size limit? Is it private?
Files up to 100MB are supported. The mid/side math runs per sample entirely in your browser - your audio never leaves your device.