Audio Channel Tool

Swap, downmix, or re-route audio channels in your browser

Pick an audio file and one operation, and ffmpeg re-routes its channels entirely in your browser — nothing is uploaded. Swap exchanges the left and right sides of a stereo file. Stereo → mono folds every channel down to one. Mono → stereo duplicates a single channel into two. Left → both and Right → both copy one side onto both channels so a one-sided recording is audible in both ears. Output is written as mp3, wav, ogg, flac, or m4a.

Worked example

An interview was recorded with the microphone plugged into the right input, so the whole conversation only plays out of the right earbud. Upload talk.wav, set Operation to Right channel → both sides and Output format to mp3, and the result out.mp3 carries that voice on both channels — usable on any speaker or phone. If the two sides were simply wired backwards instead, pick Swap left / right to put them right.

Which operation do I want?

• Swap — channels are reversed (backwards stereo mix, mis-wired cable).
• Stereo → mono — shrink a voice recording, or feed a transcription/telephony system that expects a single channel.
• Mono → stereo — force a two-channel file for a player or editor that refuses mono input.
• Left → both / Right → both — one side is silent, noisy, or the only good take; keep just that side and hear it everywhere.

Limits and edge cases

• Input files up to 10 MiB; any format ffmpeg can decode is accepted.
• swap, left, and right operate on the first two channels; on a surround source they reference the front-left/front-right channels.
• Stereo → mono uses ffmpeg's standard fold-down, so 5.1/7.1 sources are mixed with the correct channel weights, not a naive L+R average.
• Copying one side onto both (left/right) discards the other channel — the stereo image cannot be recovered afterwards, so keep your original.
• Output is re-encoded (mp3/ogg at 192 kbps; wav/flac lossless; m4a AAC). Attached album-art streams are dropped.

FAQ