Stereo to Mono
Squash to mono, spread to stereo, or pull the channels apart.
or paste one from your clipboard
How to use it
- Drop the file onto the page. The tool reads how many channels it really contains and switches off the conversions that would not make sense for it.
- Pick a direction: fold stereo down to mono, duplicate mono into a stereo pair, or split a stereo file into two separate single-channel files.
- Play it back before you commit. A downmix occasionally reveals phase cancellation that was completely inaudible in stereo, and the transport plays the converted version.
- Choose a format and download. Splitting produces two files, each listed underneath with its own download button.
What a downmix actually does
Folding stereo to mono is addition. Every sample in the left channel is added to the matching sample in the right, and the result is halved so the overall level stays where it was. That sounds harmless, and most of the time it is, but addition has a failure mode. Wherever the two channels hold the same sound at opposite polarity, adding them produces silence.
In practice this shows up as parts quietly disappearing. Wide synthesiser pads, anything that has been through a stereo widener, some reverb tails, and any effect that works by making left and right deliberately opposite all depend on that difference surviving. Collapse it and the part goes with it. Partial cancellation is more common than total: one microphone captured to two channels with a small timing offset between them will cancel at some frequencies and reinforce at others, which sounds hollow and comb-filtered rather than simply narrower. If a downmix sounds thin, that is why, and the fix is to keep one channel rather than average both. Which is what the split mode gives you.
When mono is the right answer
Speech, nearly always. A single voice recorded on one microphone has no stereo information to preserve, and storing it as two identical channels doubles the data for nothing at all. Most podcast platforms prefer mono for exactly that reason, and lossy encoders reward the choice: at a fixed bitrate, a mono file spends the entire budget on one channel and comes out audibly cleaner than the stereo version at the same setting.
Mono is also the safer choice for anything destined for a single speaker, a phone, most Bluetooth speakers, a public address system, video that will autoplay in a feed. Those devices sum to mono themselves, without asking. Doing it deliberately in advance means you discover any cancellation while you can still do something about it, rather than after publishing.
Splitting is not separating
The split mode writes each channel out as its own file. That is genuinely useful when the two channels were never a stereo image in the first place: a two-person interview with one microphone per channel, a field recorder with a lavalier on the left input and a shotgun on the right, or a backing track with a guide vocal printed to one side. Each source becomes a file you can trim, level and clean up independently.
It is not instrument separation. Left and right are the only division a stereo file contains; there is no drum channel or vocal channel hiding inside an ordinary music file, and no filter can invent one. The same limit applies in reverse. Duplicating a mono recording into two identical channels produces a file that is stereo in structure and mono in content. Which is exactly what some software and hardware demands, and nothing more than that.