Stereo to Mono Converter

A stereo file carries two separate channels — left and right — which together create a sense of width and placement. Converting to mono combines those two channels into one, so the same signal plays out of every speaker. This tool downmixes by averaging the left and right channels, the standard summing method, which preserves the overall loudness and content.

Because the two channels are summed into one, anything that was panned hard left or right ends up centered along with everything else. For the vast majority of material — speech, most music, recordings — this sounds natural and is exactly what you want when you need a single consistent channel.

Mono is the right choice whenever stereo width adds nothing: voice recordings, podcasts, phone and radio audio, transcription input, and any file that must play consistently on a single speaker. It is also the fix for the classic 'audio only in one ear' problem, and it neatly halves file size.

Keep stereo when the left-right image is part of the experience — full music mixes, binaural or ASMR recordings, field recordings where direction matters, and anything meant for immersive listening. In rare cases, summing to mono can cause phase cancellation: if the left and right channels contain the same sound but out of phase, they can partially cancel when combined, making that sound quieter. This is uncommon in normal material but is why you should give the mono result a quick listen.

At a given bitrate, a mono file stores one channel of audio where a stereo file stores two. That means a mono MP3 carries roughly half the audio data of the equivalent stereo file, so it is smaller on disk and faster to upload, email, and stream.

For content that does not need stereo — the huge category of spoken-word audio — this is a free win: you lose nothing that matters and shrink the file substantially. Across a library of voice recordings or a podcast back-catalogue, converting to mono can save a meaningful amount of storage and bandwidth.

This converter runs FFmpeg compiled to WebAssembly entirely in your browser, on your own device. Your file is read into the browser's memory, downmixed there, and offered back as a download — it is never uploaded to a server.

Once the page has loaded you can disconnect from the internet and the tool still works, which proves there is no upload step. That makes it safe for private voice recordings, unreleased audio, and confidential material.