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Stereo to Mono Converter

Fold a stereo file down to one channel by mixing both sides, or keep just the left or right one. You can also write the mono signal into both channels for players that expect stereo. Runs in your browser; no upload.

Channel mixing runs in this tab with ffmpeg.wasm. The audio file never leaves your device.

Drop an audio file here

or click to pick a track from your device

MP3, WAV, M4A, AAC, OGG, FLAC · up to 200 MB

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Three ways to make a stereo file mono

A stereo file carries two channels, left and right. Making it mono means ending up with one. The default, mixing, combines the two channels so everything in the stereo image is folded into the centre. It is the right choice for most music, interviews and field recordings, because nothing is thrown away. Left only and Right only do the opposite: they keep one channel and discard the other. Use them when one side holds a clean take and the other is noisy, or when two microphones recorded different sources and you want only one.

Mono files can be a problem on some devices. A file with a single channel may play from only one earbud or one speaker on a player, or be refused by a video editor. The option to write the mono signal into both channels solves that. The output is still a stereo container, but the left and right sides are identical, so it sounds centred and plays through every speaker.

Phase cancellation, the one real risk

Adding two channels together only works cleanly if they do not fight. If the left and right signals contain the same sound but one is inverted, the sum is silence at that frequency. This happens with some stereo wideners, with microphones placed carelessly, and with synthesizer patches that use polarity tricks for width. The result is a mono version that sounds hollow, distant or missing the bass.

Check by listening. Convert with Mix, then try Left only and Right only. If either single channel sounds fuller, use it. If the mix sounds correct, you are done. Level can differ slightly from the original after mixing, so check the loudness of the result.

When mono is useful and what to export

Spoken-word recordings gain the most. A podcast, lecture or call recorded in stereo has two nearly identical channels, so mono loses nothing and can halve the size of a WAV. Mono also suits a single public-address speaker, a mobile voice app or speech-to-text software that expects one channel. Music for headphones is better left stereo.

Sources with more than two channels are normalised to stereo first, then reduced, so surround audio is handled safely. Export MP3 for sharing, WAV for editing, or M4A for phones. Compressed formats save less space than WAV when going to mono, because the codec had already shared the data between channels.

Mono conversion guide

Which mode to choose for each situation.

Mix both channelsCombines left and right. Default for music, interviews and field recordings.
Left onlyKeeps the left channel. Use when the right side is silent, noisy or holds another source.
Right onlyKeeps the right channel. Use when the left side has the problem.
Write to both channelsCopies the mono signal to left and right so players expecting stereo play it from both speakers.
InputMono, stereo or 5.1 sources, normalised to stereo first. Up to 200 MB.
Main riskPhase cancellation can thin a mix; compare against Left only and Right only.
OutputMP3, WAV or M4A, processed entirely in this tab.

How to Convert Stereo to Mono

Three steps, all inside your browser

1

Add your audio file

Drop in an MP3, WAV, M4A, AAC, OGG or FLAC up to 200 MB. Mono files and 5.1 surround files are accepted too.

Tips: If the file is a 5.1 mix, it is brought down to stereo first and then to mono, so the result includes all channels.

2

Choose how to make it mono

Pick Mix both channels to combine left and right, or Left only or Right only to keep a single channel. Turn on the stereo output option if your player or platform insists on two channels.

Tips: If one side sounds fine and the other has noise or an unwanted voice, keep the clean side instead of mixing.

3

Apply and download

Press Apply, listen to the result and export as MP3, WAV or M4A.

Tips: Mono halves the data of an uncompressed file, so a WAV drops to about half its size. A compressed file saves less.

Stereo to Mono Questions

Mixing, single-channel extraction and the phase problem.

No. The conversion is done by FFmpeg compiled to WebAssembly inside this tab. The audio is read from your device, converted there and saved back as a download.
Mixing combines the left and right signals into one, so you hear everything that was on either side. Keeping the left or right channel copies only that side and discards the other. Use mixing for normal music and keep one channel when the other side is silent, noisy or carries a different language.
That is phase cancellation. When the same sound appears in both channels with opposite polarity, adding them together cancels it. Wide stereo effects, some synthesizers and badly recorded stereo pairs are prone to this. If the mix sounds hollow, try Left only or Right only and compare them; one of those may sound fuller than the sum.
Some players, video editors and platforms expect two channels and may play a one-channel file on a single speaker or reject it. The stereo output option copies the mono signal to both left and right so it plays through both speakers while still being identical on each side.
Yes. A file with more than two channels is first downmixed to stereo and then to mono. A file that is already mono is normalised to stereo first, so the same options apply and the output is still a single channel unless you ask for it to be written to both.
Voice recordings, podcasts, lectures, phone calls and speech for transcription are all mono in nature, and a mono file is smaller. It also suits a single speaker, public address systems and venues where a listener hears only one side. Music for normal listening should usually stay in stereo.
Mixing can slightly change the apparent level, since two channels combine into one. Check the result and use the volume booster or the audio normalizer if you want to adjust it.

Other one-click audio effects

Fix the rest of the file: volume, bass, speed, fade and more, all in the browser.

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