Free online tool

Stereo Widener Online

Widen or narrow the stereo image of any song in your browser. Width from 0 (mono) to 1.5, check mono compatibility, widen wet edits safely and export an MP3.

Open the free editor: upload MP3, WAV, AAC, OGG or FLAC, adjust speed, reverb, bass, tone, width and space, then export MP3 or a ZIP of many tracks. Everything runs in your browser.

Stereo width is how far apart the left and right channels feel. A narrow mix sounds like it is coming from a point in front of you; a wide one wraps around your head. The Width control on this editor runs from 0 to 1.5, where 1.0 is the original recording, 0 collapses it to mono and 1.5 pushes the sides out further than they were. At 1.00x speed with nothing else applied, this page is a stereo widener and a mono checker in one.

Like everything on the site, it runs in your browser with no upload, and it exports an MP3. Width is most often used as a finishing touch on slowed edits, where the slowed reverb maker presets run from 1.05 to 1.5, but it is useful on its own for any track that feels too narrow or, just as often, for checking that a wide mix still works on a single speaker. The control is documented on the stereo width control page, and because width and reverb interact, the add reverb to a song page is the natural companion.

What stereo width is

A stereo recording can be described as a mid signal (what is the same in both channels) and a side signal (what differs between them). Vocals, kick and bass usually sit in the mid. Reverb, wide synths, doubled guitars and room ambience live in the sides. A stereo widener raises the level of the side signal relative to the mid. Narrowing does the reverse. At Width 0 the side signal is removed entirely and you hear only the mid, which is mono.

That is all the Width control does. It does not add delays, does not use a Haas effect, does not create stereo from a mono file. If your source is mono, the sides are empty and Width does nothing until you add reverb, which produces a stereo tail that Width can then spread.

Width settings

Speed 1.00x, Reverb 0%, Bass 0, Tone 0 for pure width work. Width 1.5 is the Haze Chamber value, and that preset gets away with it because 54% reverb gives the sides a lot to work with.

Mono compatibility: why Width 0 matters

A lot of real-world playback is mono. Phone speakers, smart speakers, many Bluetooth speakers, shop PA systems and TikTok on a phone held in one hand all sum left and right into a single channel. When that happens, anything that is out of phase between the channels cancels out. A mix that was widened aggressively can lose its reverb, its synth pads and sometimes part of its vocal when played in mono.

Set Width to 0 and listen. What you hear is roughly what a phone speaker will deliver. If the vocal is still clear and the beat still has weight, the mix is mono-compatible. If parts go thin or disappear, your widening (or the original mix) relies on side information that mono playback throws away. Pull Width back toward 1.0 or 1.1 and check again.

This is the single most useful thing on this page for anyone making content for phones. Do it before every export.

Widening reverb-heavy edits

Reverb is mostly side information, which is why slowed + reverb edits are the natural home for the Width control. A 45% reverb at Width 1.0 sounds like a room. The same reverb at Width 1.25 sounds like a much bigger room, without touching the Reverb or Space sliders, because the tail now wraps around the listener instead of sitting behind the vocal.

Two cautions. First, widening also widens whatever stereo imperfections the source has, so a badly encoded MP3 with phasey highs gets phasier. Second, the more reverb you have, the more the mono check matters, because a wide reverb tail is exactly what cancels when summed. For slowed edits that will be heard mainly on phones, 1.1 to 1.2 is the safe band. For headphone-first YouTube uploads, 1.25 to 1.35 is fine. The guide to clear vocals in slowed edits covers how width, reverb and tone trade off.

Narrowing on purpose

Width below 1.0 is underused. Three cases where it helps:

• A vocal recording with too much room. If someone recorded in a bathroom with a stereo phone mic, Width 0.6 to 0.8 pulls the ambience in and makes the voice more direct.
• An over-wide mix that falls apart on a phone. Rather than remixing, Width 0.85 gives up a little headphone spectacle for a lot of mono robustness.
• A deliberate lo-fi or vintage feel. Width 0 with a Tone cut of -4 dB and a touch of Bass sounds like a single old speaker, which is a style in itself.

Step by step

1. Load the track. MP3, WAV, AAC, OGG or FLAC. Stereo sources only make sense here; a mono file has nothing to widen.
2. Click Dry so Speed is 1.00x and all effects are off.
3. Set Width to 0 first and listen for 20 seconds. This is your mono reference. Note what gets quieter.
4. Return to 1.0, then move to 1.1 or 1.2. Listen on headphones for the sense of space opening up.
5. Flip back to 0. If the vocal or beat is now weaker than it was in step 3, you have widened too far. Settle one step lower.
6. Export. MP3, or a ZIP for several tracks.

Cautions

• Width is not a substitute for a stereo mix. If a track was mixed narrow for a reason, widening it adds spread without adding detail.
• Width above 1.3 on a track with a wide bass can make the low end wobble in mono. Bass should stay in the centre, and most masters keep it there, but older or amateur mixes do not always.
• Headphones flatter wide mixes. Always check with Width 0 or on an actual phone speaker before posting.
• Width is applied to the whole signal. There is no way to widen only the reverb or only the high frequencies here.

Batch and presets

Add several tracks, Select All Tracks, set Width once and Download All for a ZIP. If you have a width you like for a particular style, Create preset saves it alongside Speed, Reverb, Bass and Tone in your browser's local storage on that device.

Export

MP3 at 96 kbps and 32 kHz, encoded in a web worker in your browser. Joint stereo MP3 encoding handles moderate width changes well. Extreme width at 1.5 combined with heavy reverb is the hardest case for a 96 kbps encoder, so if an export sounds swirly in the highs, pull Width back a notch. There is no WAV export; for a release, do stereo imaging in a DAW from a lossless source.