How to reverse any recording in your browser — instant
- Step 1Transfer the recording to this device — Get the voice memo or field recording onto the machine with the browser (AirDrop, cable, cloud download). Then drop the single file onto the reverser.
- Step 2Check the detected format and length — The file card shows the format-implied details: size, duration, sample rate, channels (often mono for voice memos). Confirm it is under the free-tier 50 MB / 30 minute caps.
- Step 3Press Run Reverse — FFmpeg WASM runs
-af areverseand re-encodes to the recording's own format (aacfor M4A,pcm_s16lefor WAV, and so on). No options to choose. - Step 4Wait for the in-browser pass — The whole recording is decoded and mirrored. Short voice memos finish almost instantly; a long interview takes proportionally longer because
areversebuffers the full stream. - Step 5Listen in the inline player — The result card embeds an
<audio>player on the reversed recording. Play it to confirm — reversed speech is gibberish by nature, which is normal. - Step 6Download the reversed recording — Click Download to save
recording-reversed.<ext>in the original format. Reverse it again to restore the original order if needed.
Recording formats and reversal outcome
Typical capture formats by device, and how the reverser handles each.
| Source | Usual format | Output | Lossless? |
|---|---|---|---|
| iPhone Voice Memos | M4A (AAC) | M4A | No — one AAC re-encode |
| Android recorder / messaging | M4A or OGG/Opus | Same as input | No — one re-encode |
| Field recorder (Zoom, Tascam) | WAV | WAV | Yes — exact mirror |
| High-res field recorder | FLAC | FLAC | Yes — exact mirror |
| Dictation app / older device | MP3 | MP3 | No — one MP3 re-encode |
Free vs. paid limits
Per-file caps. Duration is enforced separately from size.
| Tier | Max file size | Max duration |
|---|---|---|
| Free | 50 MB | 30 minutes |
| Pro | 200 MB | 120 minutes |
| Pro + Media | 100 GB | Unlimited |
| Developer | 100 GB | Unlimited |
Cookbook
Recipes for reversing recordings. The command shown is the WASM invocation; you only press Run.
Reverse an iPhone voice memo
Voice Memos exports M4A. The reversed output stays M4A and plays in the inline player and on any device.
Input : memo.m4a (AAC) Run : ffmpeg -i memo.m4a -af areverse -c:a aac out.m4a Output: memo-reversed.m4a
Reverse a WAV field recording losslessly
A handheld recorder's WAV reverses with an exact sample mirror — no quality loss — perfect for sound-design source material.
Input : field-ambience.wav Run : ffmpeg -i field-ambience.wav -af areverse -c:a pcm_s16le out.wav Output: field-ambience-reversed.wav (lossless)
Reverse only a quote from a long interview
Trim the segment, reverse just that, then re-merge so the rest of the interview is untouched.
Step 1 audio-trimmer -> quote.wav (/audio-tools/audio-trimmer) Step 2 audio-reverser -> quote-reversed.wav Step 3 audio-merger -> before.wav + quote-reversed.wav + after.wav
Reverse a messaging-app voice clip
WhatsApp/Telegram clips are often OGG/Opus. The reversed file keeps that format.
Input : voice-clip.opus Run : ffmpeg -i voice-clip.opus -af areverse -c:a libopus out.opus Output: voice-clip-reversed.opus
Confirm a reversal by reversing it back
Reverse the reversed recording to restore the original order — proof the operation is a true time mirror.
Pass 1 memo.m4a -> memo-reversed.m4a (backwards) Pass 2 memo-reversed.m4a -> memo-reversed-reversed.m4a (forwards again)
Edge cases and what actually happens
Reversed voice recording is unintelligible
ExpectedReversed speech is gibberish — that is the correct, normal result. Time reversal cannot reconstruct words played forwards. If you are reverse-engineering a backmasking curiosity, see play-audio-backwards-browser; any 'words' you hear are pareidolia.
M4A voice memo reversed with slight quality loss
Expected (lossy)M4A is AAC, a lossy codec. Reversal decodes and re-encodes with the aac encoder, adding one generation. It is inaudible for voice. For lossless reversal, record or export in WAV/FLAC instead.
Interview is longer than 30 minutes on free tier
Blocked (tier limit)Free caps duration at 30 minutes per file. A long interview will be blocked. Upgrade to Pro (120 min) or split it with audio-splitter and reverse the pieces.
Private recording — worried about exposure
By design (local-only)Reversal runs entirely in your browser via FFmpeg WASM. The recording is never uploaded — only an anonymous run counter updates for signed-in dashboard stats, with no audio content. Sensitive interviews and voice notes stay on your device.
Mono recording stays mono after reversal
PreservedVoice memos are often mono. Reversal preserves the channel count — a mono recording reverses to mono. It does not invent a stereo image. Use mono-to-stereo separately if you want a stereo output.
Several recordings dropped at once
Single file onlyThe reverser handles one recording per run. Reverse each separately, or merge a set of clips with audio-merger and reverse the combined file.
Want the reversed recording in a different format
By designOutput equals input format. To change it, convert afterwards — e.g. m4a-to-mp3 to turn a reversed M4A memo into MP3, or mp3-to-wav.
Very long recording exhausts browser memory
Browser limitareverse buffers the entire decoded stream in memory. A multi-hour recording can exceed a tab's memory even within size limits. Split-reverse-merge for very long captures.
Frequently asked questions
Can I reverse an iPhone voice memo without converting it first?
Yes. Drop the M4A directly — the reverser accepts M4A (AAC) and outputs M4A. It handles the decode and re-encode internally with the aac encoder, so you don't need to convert to another format first. The reversed memo plays in the inline player and downloads as name-reversed.m4a.
Are my recordings uploaded anywhere?
No. Reversal runs locally in your browser using FFmpeg 8.1 WebAssembly. Recordings — including private interviews and voice notes — are never transmitted to a server. Only an anonymous run counter updates for signed-in dashboard stats, with no audio attached.
What recording formats are supported?
MP3, WAV, FLAC, M4A (AAC), OGG (Vorbis), and Opus — covering iPhone voice memos (M4A), field recorders (WAV/FLAC), messaging-app clips (OGG/Opus), and older dictation files (MP3). The output keeps whichever format you dropped in.
Is reversing a recording lossless?
For WAV and FLAC recordings, yes — it is an exact sample mirror with a lossless re-encode. For lossy device formats (M4A, MP3, OGG, Opus), reversal adds one re-encode generation, which is inaudible for speech. Record or export in WAV/FLAC if you need bit-perfect reversal.
Why does reversed speech sound like nonsense?
Because speech isn't symmetric in time — the acoustic cues that make words intelligible only work forwards. Reversed, they become unfamiliar sounds the brain can't parse as the original words. That's expected; the reversal is accurate.
Can I reverse just one part of a long recording?
Yes — trim the section with audio-trimmer, reverse that clip here, and re-merge with audio-merger if you want it back in context. Reversal always acts on the whole file you give it.
Does it keep a mono recording mono?
Yes. Channel count is preserved, so a mono voice memo reverses to mono. If you want a stereo result, run mono-to-stereo afterwards.
How long a recording can I reverse for free?
Up to 30 minutes and 50 MB per file on the free tier. Pro raises that to 120 minutes / 200 MB. For a longer interview, split it with audio-splitter and reverse each part, or upgrade.
Can I undo the reversal?
Yes — reverse the reversed recording to restore the original order. For WAV/FLAC that's effectively the original; for lossy formats each pass is another re-encode generation, so keep the original if quality matters.
Does reversing change the speed or pitch of a voice?
No. areverse only reorders samples — same duration, pitch, and speed, just backwards. For a pitch or speed change, use pitch-shifter or tempo-changer.
Can I reverse multiple recordings at once?
Not in one run — the reverser is single-file. Reverse each recording individually, or merge a set with audio-merger and reverse the combined file.
Can I change the format of the reversed recording?
Not within the reverser — it keeps the input format. Convert afterwards with a sibling tool, e.g. m4a-to-mp3 for a reversed M4A memo, or mp3-to-wav.
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.