Load an audio file and choose whether to convert to mono or to stereo. Adjust the balance if you are expanding to stereo, press Convert and download the resulting WAV.
Mono halves the file size, guarantees that nothing disappears when a listener uses a single speaker, and fixes recordings where a microphone landed on only one channel. It is also standard for voiceovers and phone-system prompts.
The left and right channels are averaged sample by sample, which preserves the overall level and avoids the doubling you would get by simply summing them. Content that is out of phase between channels can still cancel, which is normal for any mono fold-down.
No, and it honestly cannot. Expanding mono copies the same signal to both channels so it plays correctly on stereo systems, but the extra spatial information was never recorded and cannot be invented.