Free Mono Compatibility & Phase Checker
Drop an audio file to measure stereo width and phase correlation — per frequency band — and catch low end that cancels out in mono. All in your browser, no upload.
Drop a stereo audio file here
or click to choose — WAV, MP3, FLAC, M4A, OGG
🔒 Your file never leaves your browser. Analysis runs locally with the Web Audio API — nothing is uploaded.
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That file is mono
has a single channel, so there's no stereo image or phase relationship to measure. Upload a stereo file to check mono compatibility.
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Correlation by frequency band
| Band | Correlation | Status |
|---|
Phase and width are one layer of the mix. TuneLens gives you a full AI breakdown of your mix, mastering, and sync readiness — with prioritized fixes.
Get the full AI breakdown free →What this checker measures
Phase Correlation
A single number from −1 to +1 describing how your left and right channels relate. +1 is mono, 0 is wide, and negative values mean parts of the mix will cancel when summed to mono.
Stereo Width
How much of your signal lives in the sides versus the centre, from 0% (mono) upward. Healthy mixes sit in a comfortable middle range; extreme width is often a mono-compatibility red flag.
Per-band correlation
We measure phase separately for the low, mid and high bands — because the overall number can look fine while the bass is quietly out of phase. This is where mono problems actually hide.
How to read phase correlation
Phase correlation runs from −1 to +1 and tells you what happens when your stereo mix is summed to mono. Aim to keep the meter positive — especially in the low band, where cancellation is most damaging.
| Correlation | What it means | Result in mono |
|---|---|---|
| +1 | Perfectly in phase (effectively mono) | Fully preserved |
| +0.5 to +1 | Mostly correlated, natural stereo | Safe |
| 0 | Wide and uncorrelated | Level drops ~3–6 dB |
| −0.5 to 0 | Partially out of phase | Audible cancellation |
| −1 | Fully out of phase | Cancels toward silence |
Why mono compatibility matters
A huge share of listening happens in mono or near-mono: phone speakers, single Bluetooth speakers, laptop speakers, club and venue PA systems, and many TVs. When a stereo mix is summed to mono, anything that's out of phase between the channels cancels out — so a track that sounds wide and impressive on headphones can lose its bass, vocals, or key elements entirely on a phone.
The most common culprit is out-of-phase low end, introduced by wide stereo effects, stereo reverbs on bass-heavy sources, or mis-aligned stereo recordings. Because the overall correlation can read close to zero while only the low band is the problem, the per-band breakdown above is the fastest way to spot it: if the low band is negative or near zero, your bass is at risk in mono.
Frequently asked questions
What is mono compatibility?
It's how well a stereo mix holds up when its two channels are summed to mono — which happens on phone speakers, many Bluetooth speakers, club PAs and some TVs. If parts of the mix are out of phase between left and right, they cancel when summed, so elements get quieter or disappear in mono.
What is phase correlation?
A number from −1 to +1 describing the relationship between left and right. +1 means identical (mono), 0 means wide and uncorrelated, and −1 means fully out of phase and will cancel in mono. Keep correlation positive, especially in the low frequencies.
Why does my bass disappear in mono?
Out-of-phase low frequencies are the usual cause. Wide stereo effects, stereo reverbs and mis-aligned bass can push the low band out of phase between channels, so it cancels when summed. This tool measures correlation separately for low, mid and high bands so you can see exactly where the problem is.
Is this phase checker free and private?
Yes. It's completely free with no sign-up, and runs entirely in your browser using the Web Audio API. Your audio file is decoded and analyzed locally and never leaves your device.