Load a song, voice note or sound effect, play it backwards to check, and save the reversed sound as WAV or MP3.
To reverse an audio file, add it, press Reverse and save, and the tool writes a new file in which the sound runs from the last moment to the first. Your browser first decodes the file into raw samples at your device's audio rate (often 44,100 or 48,000 Hz, shown on the page, and not always the rate of the original file), the numbers that describe the sound wave, one list per channel. Reversing means reading each list from its last number to its first, on the left and right channel at the same time, so a stereo sound keeps its balance. The length does not change: a 10-second sound is still 10 seconds, and a drum hit that ended the sound now starts it. Press Play reversed first if you want to hear the result before saving. The original file is never changed, and the sound is never uploaded; the work happens in this tab, in a background worker, so the page stays responsive.
Leave the Start and End boxes empty to reverse the whole file, or type times to reverse just one part. Times are written minutes:seconds.milliseconds, so 1:23.5 is one minute and 23.5 seconds, and a plain 83.5 means 83.5 seconds. With a start of 0:02 and an end of 0:05, the saved file holds only those 3 seconds, played backwards; the rest is dropped, not kept. The end must be after the start by at least 0.05 seconds and cannot pass the end of the sound. If you want the backwards part inside the longer sound, reverse the part here and join the pieces afterwards with an audio joiner.
WAV has no MP3-style compression: it stores every sample as 16-bit PCM (a sound decoded at a higher precision is rounded to 16 bits), and the size is easy to work out: 44 bytes of header plus the number of samples times the number of channels times 2. A 10-second stereo sound at 44.1 kHz is 44 plus 441,000 times 2 times 2, which is 1,764,044 bytes, about 1.7 MB. MP3 compresses the sound with the LAME encoder, compiled to WebAssembly and loaded only when you first save as MP3. At a constant 192 kbps the same 10 seconds is about 240,000 bytes. If the original was already an MP3 or an M4A, saving as MP3 compresses it a second time, so choose WAV when quality matters and convert later.
The whole file is decoded in memory, so a file may be up to 100 MB, and the decoded sound plus the reversed copy must fit a memory budget. That is about 7 minutes of 48 kHz stereo on a computer and about 3 minutes on a phone or tablet; mono at a lower sample rate fits about twice as long, up to 30 minutes. Longer sounds are refused with a message that says so. A file with more than two channels is mixed down to stereo first. Four-channel (quad) and 5.1 files use the Web Audio API equations, so the centre and rear channels are heard and the LFE channel is left out. Any other channel count has no standard layout, so every channel is mixed equally into both sides. Tags such as the title, the artist and cover art are not copied, because the sound is rewritten from samples. Reversing does not change the pitch or the speed. Some browsers cannot play OGG, and then that file is refused with a clear message.
Add the MP3, press Play reversed to listen, then press Reverse and save. A 3-minute stereo song saved as WAV is about 30.3 MB (44 bytes plus 180 s times 44,100 samples times 2 channels times 2 bytes = 31,752,044 bytes); as MP3 at 192 kbps it is about 4.1 MB (4,320,000 bytes). Sizes use 1 MB = 1,048,576 bytes.
No. The file is decoded, reversed and written inside this browser tab, with background workers on your device. The sound, its name and its tags never leave the tab. Like the rest of this site, the page sends an anonymous usage event to Google Analytics with a rough file-count and file-size bucket, but never the file or its name. Closing the tab clears the sound.
Yes. Type a start and an end in the two boxes, for example 0:02 and 0:05, and only those 3 seconds are saved, backwards. Empty boxes mean the whole file. The end must be at least 0.05 seconds after the start.
Reversing only reorders samples, so the pitch and speed stay the same. WAV is saved as 16-bit PCM without MP3 compression, but a 24-bit source is rounded to 16 bits, and your browser decodes every file at your device's audio rate (often 44,100 or 48,000 Hz), so a file with another rate is resampled first. The page shows the rate that will be saved. Saving as MP3 compresses again: at 192 kbps that is a small, usually inaudible, loss.
Up to 100 MB, and about 7 minutes of 48 kHz stereo on a computer or about 3 minutes on a phone or tablet. Mono and lower sample rates fit longer sounds, up to 30 minutes. Longer files are refused with a message.
Speech sounds have a sharp start and a slow fade. Played backwards the fade comes first and the sharp start last, so consonants like t and k land at the end of each sound. That is why a 2-second phrase can sound foreign when reversed, and reversing the reversed file turns it the right way round again. It will not be sample-for-sample identical, because saving as WAV rounds to 16 bits, the browser may resample, and MP3 is lossy.