Stereo Widener Online
Widen the stereo image of any audio file in your browser. Pick Subtle, Wide, or Extra Wide mid/side processing — instantly get a bigger, more spacious sound, no sign-up, no upload.
Widen Stereo in 3 Steps
No knobs, no listening tests. Drop, pick, download.
Upload Your Audio
Drag and drop a stereo MP3, WAV, or other audio file. Up to 200 MB.
Pick a Width
Tap Subtle, Wide, or Extra Wide. Wide is the default for most material.
Widen & Download
Hit Widen stereo, preview the result, then save a clean MP3 or WAV to your device.
Why Notevibes Stereo Widener
True mid/side widening, center kept solid.
Mid/Side Widening
Pure mid/side processing keeps the center solid while pushing the sides out — a bigger image, not a hollow one.
One-Click Width
Pick Subtle, Wide, or Extra Wide — the width is applied sample-by-sample in seconds. Drop, pick, download.
Private In-Browser
Audio is processed locally in your browser using the Web Audio API. Nothing is uploaded.
Preview Before Download
Hear the widened result inline before you save it. Tweak the width and re-preview as many times as you like.
Export MP3 or WAV
Save the widened audio as a clean MP3 or lossless WAV — no watermark, no ads, no attribution.
Works on Mobile
Widen stereo on your phone or tablet. iOS, Android, Chrome, Firefox, Safari, Edge.
Your Audio Stays on Your Device
Every file is processed locally in your browser using the Web Audio API. Nothing is uploaded, stored, or analyzed.
No Upload
File never leaves your device
No Account
Start widening immediately
No Tracking
We never see your audio
When to Widen Stereo
Most files process in under a second.
Widen a music mix
Open up a flat, narrow mix into a spacious stereo field
Bigger podcast intro
Make a music bed or stinger feel wide and cinematic
Spacious ambience
Spread room tone and pads into an immersive backdrop
Widen synths & pads
Push synths and pads to the edges without losing the center
Collapse to mono
Use the Mono preset to check and fix mono compatibility
Game & film sound design
Build a wider sense of space for effects and atmospheres
Need Full Tone Shaping?
The Notevibes Audio Editor stacks stereo widening with EQ, bass boost, compression, limiter, and effects — process whole tracks in one pass.
Open Full Audio EditorConvert Any Audio Format
Free browser-based converters for every major audio format — no sign-up, no upload.
Related Audio Tools
More free browser audio tools from Notevibes — no sign-up, no upload.
Mono to Stereo Converter
Convert mono audio to 2-channel stereo.
Stereo to Mono Converter
Downmix stereo audio to a single mono channel.
Audio Normalizer
Boost audio to peak volume without clipping.
High-Pass Filter
Cut low-frequency rumble below a chosen frequency.
Low-Pass Filter
Cut high-frequency hiss and harshness above a cutoff.
Online Audio Editor
Multi-track browser editor with every tool built in.
Frequently Asked Questions
How does the stereo widener work?
It uses mid/side processing. Your stereo signal is split into a mid (center) channel and a side (difference) channel. The widener multiplies the side channel — by 1.2 for Subtle, 1.5 for Wide, or 1.8 for Extra Wide — so the parts panned away from center get pushed further out while the center stays put.
What does the width value control?
It's how much the side channel is amplified. Subtle (1.2) is a gentle lift, Wide (1.5) is the default for most material, and Extra Wide (1.8) is dramatic. Mono (0) removes the side channel entirely, collapsing the track to a centered mono image.
Does it work on mono files?
No. Stereo widening needs a stereo (two-channel) track because it works on the difference between the left and right channels — a mono file has no side signal to widen. If you upload a mono file, the tool will tell you and the widen step will be skipped.
Will it cause phase issues?
Widening boosts the side channel, which can reduce mono compatibility — if a track is summed to mono later, very wide content can partially cancel out. Stick to Subtle or Wide for material that may be played on phone speakers or in mono, and use the Mono preset to check how it collapses.
Is the stereo widener free?
Yes. Completely free with no sign-up, no watermark, and no limits. Max file size is 200 MB.
Is my audio file uploaded to a server?
No. The stereo widener runs entirely in your browser using the Web Audio API. Your file never leaves your device — nothing is uploaded, stored, or analyzed.
What audio formats are supported?
MP3, WAV, M4A, FLAC, OGG, and AAC. Anything your browser can decode via the Web Audio API will load. You can export the widened result as MP3 or WAV.