How to reverse any audio file online — free, no upload
- Step 1Drop your audio file onto the dropzone — Drag in any single audio file — MP3, WAV, FLAC, M4A, OGG, or Opus. The reverser takes one file at a time (no batch on this tool). The file is read into memory locally; nothing uploads.
- Step 2Check the detected file details — The file card shows size, duration, sample rate, and channel count (mono / stereo) read from the decoded header. Use this to confirm the free-tier 50 MB / 30 min limits before running — duration is checked separately from size.
- Step 3Press Run Reverse — There are no options to set. FFmpeg loads (a one-time WASM fetch), then runs
ffmpeg -i input -af areverse -c:a <encoder> output. The encoder is chosen automatically from your file's format. - Step 4Wait for the single in-browser pass — Because
areversebuffers the whole stream, processing scales with file length. A typical 3–4 minute song reverses in a few seconds on a modern laptop; a 25-minute lecture takes longer and uses more memory. - Step 5Audition the reversed result — The result card embeds an
<audio>player on the reversed output plus a metrics strip (input bytes, output bytes, time, engine). Play it to confirm the reversal sounds right before you save. - Step 6Download the reversed file — Click Download. The file is saved as
yourname-reversed.<ext>with the same extension as the input. To undo, just reverse the reversed file — two passes return you to the original sample order.
Per-format reversal behaviour
What areverse does for each accepted input. Output format always equals input format; the re-encode is lossless only where the codec is lossless.
| Input format | Output format | Re-encode codec | Lossless? |
|---|---|---|---|
WAV (.wav) | WAV | pcm_s16le | Yes — exact sample mirror; PCM round-trips bit-for-bit |
FLAC (.flac) | FLAC | flac | Yes — FLAC is a lossless codec; reversal is exact |
MP3 (.mp3) | MP3 | libmp3lame | No — decode + reverse + re-encode adds one lossy generation |
M4A / AAC (.m4a) | M4A (AAC) | aac | No — lossy AAC re-encode |
OGG Vorbis (.ogg) | OGG | libvorbis | No — lossy Vorbis re-encode |
Opus (.opus) | Opus | libopus | No — lossy Opus re-encode |
Tier limits for the reverser
Reversal is a free-tier operation. Limits are per file; duration is enforced separately from size because areverse must buffer the whole stream.
| Tier | Max file size | Max duration | Files per run |
|---|---|---|---|
| Free | 50 MB | 30 minutes | 1 |
| Pro | 200 MB | 120 minutes | 1 (this tool is single-file) |
| Pro + Media | 100 GB | Unlimited | 1 (this tool is single-file) |
| Developer | 100 GB | Unlimited | 1 (this tool is single-file) |
Cookbook
Concrete reversal recipes. The command shown is the exact FFmpeg invocation the tool runs in WASM; you do not type it — the UI builds it.
Reverse a WAV losslessly
A 24-bit/48 kHz WAV stem reversed for a production. The PCM mirror is exact and the WAV re-encode preserves every sample, so this is a true lossless reversal.
Input : stem.wav (WAV, 48000 Hz, stereo) Run : ffmpeg -i stem.wav -af areverse -c:a pcm_s16le out.wav Output: stem-reversed.wav (same format, exact mirror) Reverse it again -> stem-reversed-reversed.wav == original samples
Reverse an M4A from a phone
An iPhone voice memo or AAC export comes in as M4A. The output stays M4A (AAC), so it plays everywhere the original did — but note the AAC re-encode is one lossy generation.
Input : memo.m4a (AAC) Run : ffmpeg -i memo.m4a -af areverse -c:a aac memo-reversed.m4a Output: memo-reversed.m4a (AAC, reversed)
Want a different output format than the input?
The reverser cannot change format — it always emits the input's format. To reverse AND convert, do it in two steps using the matching sibling converter, then reverse.
Goal: reversed MP3 from a WAV source Step 1 wav-to-mp3 -> song.mp3 (/audio-tools/wav-to-mp3) Step 2 audio-reverser on song.mp3 -> song-reversed.mp3 (Reverse first if you'd rather keep WAV quality through the reversal, then convert the reversed WAV with wav-to-mp3.)
Reverse just a section, not the whole file
areverse reverses the entire file. To reverse only a phrase, trim it out first, reverse the clip, then re-merge around it.
Step 1 audio-trimmer -> phrase.wav (the 4s you want backwards)
Step 2 audio-reverser -> phrase-reversed.wav
Step 3 audio-merger -> intro.wav + phrase-reversed.wav + outro.wav
(/audio-tools/audio-trimmer, /audio-tools/audio-merger)Build a reverse-reverb swell (3-pass)
The classic reverse-reverb effect needs a reverb step this tool does not provide — but it does the two reversal passes. Add the reverb in your DAW between them.
1. audio-reverser -> vocal-reversed.wav 2. (in your DAW) apply reverb to vocal-reversed.wav -> wet.wav 3. audio-reverser -> wet-reversed.wav Result: reverb that swells UP into each word instead of trailing after it.
Edge cases and what actually happens
You expected an MP3 but got back the input's format
By designThe reverser has no format selector. It re-uses the input file's extension for the output, so a WAV in gives a WAV out. This is deliberate — it avoids silently transcoding your audio. If you need a different container, run a sibling converter such as wav-to-mp3 before or after reversing.
Reversing an MP3 is not bit-perfect
Expected (lossy codec)MP3, M4A/AAC, OGG, and Opus are lossy. Reversal decodes the file, mirrors the samples, and re-encodes — that re-encode is a fresh lossy generation. The loss is small at the same bitrate but it is not zero. For a truly lossless reversal, work in WAV or FLAC.
File is longer than 30 minutes on the free tier
Blocked (tier limit)Free tier caps duration at 30 minutes per file, independent of the 50 MB size cap — a long, low-bitrate file can pass the size check but fail on duration. Upgrade to Pro (120 min) or split the file with audio-splitter, reverse the pieces, and re-merge in reverse order.
Very long file runs out of memory
Browser limitareverse cannot stream — it must hold the whole decoded PCM stream in memory to emit the last sample first. A 90-minute uncompressed file can exceed a tab's memory budget even within a paid size cap. Close other tabs, or split-reverse-merge. This is a property of the filter, not a JAD restriction.
You dropped multiple files at once
Single file onlyThe reverser accepts one file per run — there is no batch dropzone on this tool. Reverse each file individually. If you need to reverse the playback order of several clips concatenated together, merge them first with audio-merger, then reverse the single merged file.
Reversed speech sounds like gibberish
ExpectedReversed human speech is not intelligible — that is normal. The tool mirrors samples in time; it does not, and cannot, reconstruct words played forwards. For backmasking curiosity, listening to reversed speech, see play-audio-backwards-browser.
Reversing the reversed file restores the original
By designReversal is its own inverse. Running the tool twice returns the original sample order. For lossless formats (WAV/FLAC) the double pass is essentially the original; for lossy formats each pass adds a re-encode generation, so two passes is two generations of loss.
Output filename has a -reversed suffix
ExpectedThe download is named original-reversed.<ext> so it never overwrites your source. The extension matches the input. If you reverse twice you will get ...-reversed-reversed.<ext>.
FFmpeg WASM takes a moment to load on first run
ExpectedThe first reversal fetches the FFmpeg core into the browser. Subsequent runs reuse the loaded engine and start instantly. The engine strip at the top shows whether multi-threaded (MT) FFmpeg and WASM SIMD are active, which affects speed.
Frequently asked questions
Is reversing audio with this tool lossless?
It depends on the format. For WAV and FLAC, yes — reversal is an exact sample-by-sample mirror and the lossless re-encode preserves every bit, so the output is identical to a forwards-played-backwards original. For MP3, M4A/AAC, OGG, and Opus, the file must be decoded, reversed, and re-encoded; that re-encode is a single lossy generation. Work in WAV or FLAC if you need a bit-perfect reversal.
Does my file get uploaded anywhere?
No. The reverser uses FFmpeg 8.1 compiled to WebAssembly and runs entirely inside your browser tab. The audio is read into memory locally, reversed, and offered back as a download. Nothing is transmitted to a server — only an anonymous run counter updates for signed-in dashboard stats, which carries no file content.
Can I choose the output format?
No — and that is intentional. The reverser always emits the same format you dropped in (WAV in, WAV out; M4A in, M4A out), so it never silently transcodes your audio. If you want the reversed file in a different format, run a sibling converter such as wav-to-mp3 or m4a-to-mp3 before or after reversing.
What formats can I reverse?
MP3, WAV, FLAC, M4A (AAC), OGG (Vorbis), and Opus. Each is decoded, reversed with FFmpeg's areverse filter, and re-encoded back to the same format using the matching codec (pcm_s16le for WAV, flac for FLAC, libmp3lame for MP3, aac for M4A, libvorbis for OGG, libopus for Opus).
How long can the file be?
Free tier allows up to 30 minutes and 50 MB per file. Pro raises this to 120 minutes / 200 MB. Pro + Media and Developer remove the duration limit. Duration is checked separately from size because areverse has to buffer the whole stream — a long, low-bitrate file can pass the size check yet still be too long.
Why is there no preview before I run it?
Reversal is a single deterministic operation with no settings, so there is nothing to preview-tune. Instead, the tool gives you a player on the *result*: after it runs, the reversed file plays inline in the result card so you can audition it before downloading.
Can I reverse only part of a file?
Not in one step — areverse reverses the whole file. To reverse a section, trim that section out with audio-trimmer, reverse the clip here, then stitch it back with audio-merger.
How do I undo a reversal?
Reverse the reversed file. Reversal is its own inverse, so a second pass restores the original sample order. For WAV/FLAC that is effectively the original; for lossy formats each pass adds one re-encode generation.
Will reversing change the pitch, speed, or length?
No. areverse only reorders samples — same duration, same sample rate, same pitch, same channel count. If you want to change pitch or speed, use pitch-shifter, time-stretcher, or tempo-changer.
Can I batch-reverse many files?
Not on this tool — it processes one file per run. Reverse files individually, or merge them first with audio-merger and reverse the single result if you want them back-to-front as one track.
Does it work offline?
After the first run loads the FFmpeg WASM core, the actual reversal runs locally with no network dependency. The initial engine fetch needs a connection; once cached, repeat reversals work without re-fetching.
Is it really free?
Yes. audio-reverser is a free-tier tool — the reversal itself is not Pro-gated. Pro only raises the file-size and duration ceilings (200 MB / 120 min) for very large or long files.
Privacy first
Every JAD Audio tool runs entirely in your browser via FFmpeg (WebAssembly) and RNNoise. Your audio files never leave your device — verified by zero outbound network requests during processing.