Free Online Stereo Widener
Make a mix wider or narrower with mid/side processing from 0 to 200%, keep the bass mono below a cutoff, and watch a live correlation meter.
Source
Loops while you adjust. Match loudness sets the effect to the same average level as the original while previewing, so you judge the tone and not the volume. It does not change the export.
Stereo widener
Drag a knob up or down, or focus it and use the arrow keys. Double-click or press Delete to reset one knob.
Meters
+1 is mono, 0 is very wide, below 0 can cancel on mono speakers.
The safety limiter only protects the preview. The export is turned down as a whole if needed, so peaks stay under -1 dBTP.
Export
How to use the stereo widener
How to use it
The tool splits the audio into mid (what both speakers share) and side (the difference between them). Width scales the side signal: 0% is mono, 100% is unchanged, 200% doubles the side.
Mono below removes side content under the cutoff, so kick and bass stay centred and solid.
Sensible starting settings
- Gentle widening for a full mix: width 115 to 130%, mono below 120 Hz.
- Tighten a messy low end: width 100%, mono below 150 to 200 Hz.
- Check mono safety: set width to 0% for a moment to hear the mix in mono.
Watch the correlation meter
The meter reads +1 for mono and 0 for very wide audio. If it often drops below 0, parts of the mix will get quieter or vanish on phone speakers and mono club systems. Back off the width until it stays mostly above 0.
Exports a 24-bit WAV.
How it works.
- 1
Drop in a file
MP3, WAV, FLAC or M4A. It is decoded on your device.
- 2
Adjust while it plays
Turn the controls and hear the change live. Use bypass and loudness match to compare fairly.
- 3
Save a 24-bit WAV
Render the full file and download it with your plan access. Your original is unchanged.
Questions.
Does it work on mono files?
A mono file has no side signal, so widening does nothing. This tool only changes width that already exists in a stereo file.
Is widening to 200% safe?
Not always. Strong widening can cause cancellation in mono. Watch the correlation meter and check with width at 0%.
What does mono below do?
It applies a 24 dB per octave high-pass filter to the side signal only, so everything under the cutoff plays the same in both speakers.
Will it change the loudness?
Widening adds side energy, so the file can get slightly louder. Use Match loudness while comparing. The export is turned down if needed to stay under -1 dBTP.
Is my audio uploaded?
No. The file is decoded and processed in your browser with the Web Audio API. Nothing is sent to a server.
Can the export clip?
No. After rendering, the tool estimates the true peak between samples. If it would go above -1 dBTP, the whole file is turned down by the amount needed, and that amount is shown.