Duplicate a mono audio file onto two identical channels (left + right) - for software or devices that strictly expect stereo. No upload.
Running locally on your device ...
Running locally on your device ...
0%
Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
Some video editors, some upload forms and some older playback devices strictly require a stereo audio track and either reject a single-channel mono signal or behave unexpectedly with it. This tool solves exactly that problem by copying the one mono channel identically onto left and right - technically the counterpart to the existing "Stereo to mono" tool.
Important to understand: the result is not a "real" stereo experience with spatial width - left and right stay sample-for-sample exactly identical. Anyone looking for an artificial stereo-widening effect with delay or phase differences needs a different, much more elaborate tool. This tool solves only the compatibility problem "software expects two channels".
Only genuinely mono files are accepted; an already multi-channel source gets a clear message instead of a guessed result. Processing runs entirely locally in the browser.
| Input formats | MP3, WAV, M4A, AAC, OGG, OPUS, FLAC |
|---|---|
| Auto-conversion | MP4 |
| Output formats | WAV, M4A |
| Batch processing | No |
| Processing | Locally in your browser (WebCodecs) |
| File upload | None |
Limitations: True mono files only (exactly 1 channel) - an already multi-channel source is refused with a clear message. Left and right are then identical (no artificial spatial effect). Honest per-device length cap (desktop about 20 minutes, tablet 15, phone 10). Compressed inputs need the browser WebCodecs decoder.
No, everything stays local in the browser.
No. Left and right are identical - this is about compatibility, not a spatial effect.
With already multi-channel material it would be unclear what to duplicate - an honest refusal beats a guessed result.
Yes, the sibling tool "Stereo to mono" downmixes two channels to one.
Reverse audio · Split audio · Strip metadata · Stereo to mono · Swap left/right