How to reverse audio
- Drop an MP3, M4A, WAV, FLAC, OGG or Opus file, or press Record with the microphone, say or sing something and press Stop.
- Listen to the original in the player if you like, and choose how to save it: MP3, M4A or WAV.
- Press Reverse audio. The backwards version appears in a player with a download button.
- Reverse this result again turns it forwards once more, handy for checking or for the challenge below.
The reverse singing challenge
The game goes like this: take a short line of a song, play it backwards, record yourself copying the backwards sound as closely as you can, then reverse your recording. If you copied it well, the song comes out forwards, a little strange. On this page that is three steps without leaving it:
- Drop the clip (or record someone singing it) and reverse it. Listen a few times.
- Press Record and imitate what you heard, then Stop.
- Press Reverse audio on your recording and play the result.
Two details make it work better. The microphone records with the browser’s voice processing switched off: we measured that Chrome’s default noise suppression fades a held note by about 8 dB within eight seconds, and backwards that fade turns into an odd swell. And keep the line short, three to five seconds; nobody can copy a long backwards phrase.
What we checked
| File | Result |
|---|---|
| WAV, 6 seconds, 16-bit | every one of 264,600 samples is the original’s mirror image; reversed twice it is identical to the original |
| MP3, 128 kbps | same length to the sample and lined up with the original to 0 samples; the encoder delay and padding are removed, so no silence is added at the start or end |
| iPhone Lossless voice memo (24-bit) | saved as 24-bit WAV, every sample mirrored |
| 3-second microphone recording | reversed and saved as MP3 |
The page checks each result itself: it decodes the new file and compares it, sample by sample from the end, with the original. With WAV the check says every sample matches. With MP3 or M4A the sound has to be encoded again, and the box tells you how far below the sound that encoding difference is.
MP3 or WAV?
Each MP3 encode loses a little. In our test, an MP3 reversed once differed from the mirrored original by a level 26 dB below the sound, and reversed back again by 20 dB: the second copy is audibly closer to the noise. If you are going to reverse a file more than once, or keep editing it, save it as WAV, which is lossless; turn it into an MP3 at the very end with WAV to MP3. For sharing a single reversed clip, MP3 is fine.
Reversing changes only the order of the sound: the length, the pitch and the loudness stay the same. To change the speed or the pitch instead, use Change Audio Speed; to cut out the part you want first, Trim Audio; to record without reversing, Voice Recorder; for a video that plays backwards, Reverse Video. Nothing is uploaded: the file and your recording stay in your browser.