Reverse audio so it plays backwards

How to use the audio reverser

1. Add the audio file you want to flip. MP3, WAV, M4A, OGG, FLAC and WebM all work, as does the audio track of MP4, MOV or MKV video.
2. Optionally change Save as. WAV (16-bit, lossless) is the default; M4A (AAC), WebM (Opus) and OGG (Opus) show a Bitrate choice from 64 to 320 kbps.
3. Press Reverse.
4. Play the result in the page and download it. The file name ends in -reversed.

What it does and when to use it

Reversed sound has an unmistakable shape: notes swell up from silence and cut off sharply. Producers use it for risers into a chorus, reversed vocal chops and dream-like intros. Sound designers reverse footsteps, voices and impacts for science-fiction or horror effects. Teachers use it in physics and music lessons to show how much of a sound’s identity lives in its attack. Some people simply want to hear what a song sounds like backwards.

A short source works best. Cut one hit or phrase with the audio trimmer before reversing. Add a gentle start with audio fade in and out, and lay the reversed piece in front of the original with the audio merger.

How it works

After decoding in a Web Worker, each channel is a list of numbers, one per sample. The tool copies every list and reverses its order: for a 2.5-second clip at 44,100 Hz, sample 110,249 becomes sample 0. Left stays left and right stays right, so the stereo picture is unchanged. No filtering, resampling or level change happens. The new list is then written as WAV directly, or encoded to AAC or Opus with your browser’s WebCodecs encoder. Nothing is uploaded.

Worked example

Running the tool on a 2.5-second mono test file at 44.1 kHz gives:

• Summary: “Reversed 0:02.50”
• Reversed 0:02.50 and Length 0:02.50, the same as the input
• File size 215.4 KB as 16-bit WAV, saved as cymbal-reversed.wav

Saved as OGG at 192 kbps (about 24 KB per second) it would be far smaller, but some browsers cannot encode Opus. If the encode fails, the tool says so and you can choose M4A or WAV.

Limits and tips

• Reverse reverb trick: reverse a vocal, add reverb in your editor, then reverse it again here. The echo now rises into each word.
• Long tracks are decoded in full before reversing, and a minute of stereo takes about 21 MB of memory, so a full album side may be too much for a phone.
• Formats other than WAV depend on WebCodecs in your browser (Chrome, Edge, Firefox, or Safari 26+). AIFF, AMR, WMA and CAF, and MP3 output, need the optional ffmpeg fallback: a one-time download of about 30 MB from cdn.jsdelivr.net, and your file still stays on your device.