Unreverse audio

Unreverse means: take a file that already plays backwards, reverse it again, and hear the forward performance. On this site that is not a special codec. It is the same time-reverse engine, second pass.

If the original buffer is still in the open tab, you do not need a second pass at all. Use Normal to hear the source direction and Reverse to hear backwards. That A/B does not re-encode. Details: audio normal. Unreverse as a file operation starts when you only have the reversed WAV (or MP3) on disk.

Why a round trip is not bit-perfect

A mathematically exact reverse of a reverse returns every sample. Real tools add small windowing so the first and last samples do not click against silence or against a DAW cut.

This editor applies a short fade at the edges of the reversed buffer to reduce those clicks. After two passes, the samples near 0 and near N-1 are not identical to the first file you uploaded. The middle of a voice note—the words—come back. The one or two milliseconds at the boundaries do not.

Other non-identity sources:

• The browser decoded MP3/AAC/OGG into PCM, then you downloaded WAV, then you re-uploaded. You never had bit-identical PCM of the lossy file to begin with.
• AudioContext sample rate might resample a 44.1 kHz file to 48 kHz (or the reverse) depending on the device. The restored WAV may be a different rate than the first upload.
• A second WAV encode is still PCM, but if anything dithered or converted, bits move.

For forensic “prove this is the same take,” keep the original upload. Do not rely on unreverse as an archive strategy. For “I can hear the joke again,” unreverse is enough.

High-quality reverse is about the one-way WAV out, not about lossless round trips.

How to unreverse a file

1. Upload the reversed clip (MP3, WAV, FLAC, OGG, M4A, or AAC).
2. Play. If you already hear forward speech, you uploaded the original by mistake.
3. If you hear reverse, wait for the process—you want another reverse, which is the default mode.
4. Download the new WAV. Label it restored so you do not stack names.

If someone sent you a reversed puzzle, this is the decode step. If you reversed a Voice Memo and deleted the memo, this is the recovery step for word order, not for the memo’s original encoder delay or loudness metadata.

Microphone: only if you are re-recording a reversed playback off speakers, which is a bad unreverse (room noise, clock drift). Always upload the file.

Sixty-second record is irrelevant unless you are creating a new take.

Speed preview does not belong on a restoration. Leave rate at 1× when judging whether words came back.

What unreverse will not undo

• Polarity invert done in a DAW (phase invert)
• EQ, compression, or a “reverse filter” that was actually a plugin chain (reverse audio filter)
• Pitch shift, autotune, or a voice changer
• Missing data from a truncated WhatsApp export
• A video whose picture was reversed in another app—this site never had the picture

Flip audio means time reverse here; flipping twice is unreverse, not an L/R restore. If someone swapped stereo in a DAW, reverse will not put L and R back.

Spanish-language “inverter” queries are still time reverse: inverter audio online. Inverting twice is the same idea as unreverse.

Workflow hygiene

Keep take.wav and take_rev.wav. Do not overwrite the only copy with a second reverse until you have heard it. Edge fades accumulate if you reverse six times “for luck”; do not.

If you need a truly reversible process in production, reverse in a DAW with reverse disabled on export of the session, or freeze a reverse plugin that you can bypass. This website is a one-buffer utility.

Local processing: the restored WAV is yours. Nothing is stored as an “undo history” in an account. Close the tab and unsaved buffers are gone—another reason Normal mode during the first session is cheaper than a later unreverse.

Forensic versus practical restore

Practical: you hear the joke forward again. Good enough for chat and class.

Forensic: you need hashes to match the pre-reverse file. Unreverse will fail that test. Produce the original from backup, camera card, or Voice Memos. Do not send an unreversed WAV to a process that expects the camera original.

Stacked reverses (reverse → send → they reverse → send → you reverse) nibble fades each time. After a few trips the edges sound soft. That is not “generation loss” in the MP3 sense if you stayed in WAV, but the fades still accumulate.

Labeling so you do not unreverse the original

If final.wav is already forward, reversing it “to unreverse” makes a backwards file and you made the problem you were solving. Listen first. If it is already English in the right order, stop.

A header comment in a text note next to the folder is more reliable than memory. This website will not write a REVERSED=true chunk into the WAV.

Mic-to-speaker “unreverse” (playing reverse on speakers, recording with the laptop) adds room and clock drift. Never use it when you have the file.