How to silence sensitive information in recordings — free tool
- Step 1Open the redactor and drop your recording — Drop the recording into the redactor. Audio formats are accepted (MP3, WAV, FLAC, M4A, OGG, Opus); Pro-tier covers up to 200 MB and 120 minutes per file.
- Step 2Let the file decode in your browser — The tool decodes the audio locally to read its duration. Nothing is uploaded — FFmpeg 8.1 runs as WebAssembly inside the page, so the recording never leaves your device. The decoded duration becomes the upper bound for every range you add.
- Step 3Add a redaction range — Click Add range. A row appears with Start and End number inputs (in seconds). A new range defaults to 0 s to 1 s; type the real start and end of the segment you want silenced.
- Step 4Mark every segment that needs silencing — Add a range for each sensitive segment — a spoken password, a confidential number, an off-record comment. Pad slightly on each side so the whole utterance is captured. There is no detector; your judgement defines the boundaries.
- Step 5Process the file — Run the tool. For each range it applies
volume=0gated tobetween(t, start, end), so the audio inside every marked range becomes pure silence. The rest of the timeline is untouched and the file is re-encoded to the output format. - Step 6Download and verify — Play the
-redactedoutput across every boundary to confirm the sensitive content is fully gone and nothing useful was muted by accident. Adjust ranges and re-run from the original if needed.
What the redactor actually does
Every row verified against the browser processor and the range UI. The tool mutes — it does not bleep, beep, or insert noise.
| Behaviour | Implementation | What it means for you |
|---|---|---|
| Redaction method | Volume set to 0 (full silence) inside each marked range via the FFmpeg volume filter with an enable='between(t,start,end)' gate | No tone, beep, or noise is inserted — the range goes silent |
| Marking | Manual only — you add ranges with Add range and type Start and End in seconds | There is no auto-detection, transcription, or phone-number finder in the tool |
| Time granularity | Start/End inputs step in 0.1 s (100 ms) increments | Type a finer value directly if your browser allows; the filter uses your exact number |
| Range bounds | Each input is clamped to min 0 and max = the file's decoded duration | You cannot mark a range past the end of the file |
| Output format | Defaults to the input file's extension and is re-encoded through FFmpeg | Lossy inputs (MP3/M4A/OGG/Opus) are re-compressed; WAV/FLAC stay lossless |
| Filename | Original name with a -redacted suffix | e.g. interview.mp3 becomes interview-redacted.mp3 |
| Empty input guard | Throws Add at least one redaction range if no range is set | At least one Start/End pair is required before processing |
Input and output formats
Output is re-encoded through FFmpeg 8.1 (WebAssembly). The output extension follows the input by default; the encoder is chosen from that extension.
| Format | Output encoder used | Lossy on re-encode? |
|---|---|---|
| MP3 | libmp3lame | Yes — re-compressed (one extra lossy generation) |
| WAV | pcm_s16le | No — lossless PCM |
| FLAC | flac | No — lossless |
| M4A / AAC | aac | Yes — re-compressed |
| OGG (Vorbis) | libvorbis | Yes — re-compressed |
| Opus | libopus | Yes — re-compressed |
Audio tier limits that apply to redaction jobs
PII redaction runs inside the audio tool family, so the audio family limits apply. Numbers are per the live tier table; durationMin is a per-file duration cap that is separate from the file-size cap.
| Tier | Max file size | Max duration / file | Files per job |
|---|---|---|---|
| Free | 50 MB | 30 min | 1 |
| Pro | 200 MB | 120 min | 10 |
| Pro-media | 100 GB | Unlimited | 100 |
| Developer | 100 GB | Unlimited | Unlimited |
Cookbook
Recipes for muting confidential spoken content in place. Times are seconds you type into Start/End.
Mute a spoken password in a screen-share recording
Someone read a password aloud at 1:12. Silence just that phrase while keeping the rest of the walkthrough intact.
Range: Start: 71.6 End: 74.0 The password phrase is muted; the walkthrough before and after is untouched; total length unchanged. Output: walkthrough-redacted.mp3
Blank a confidential figure in a recorded briefing
A revenue figure that should not be circulated is stated at 8:40. Mute it but keep the briefing aligned for the team that gets the timestamped notes.
Range: Start: 519.0 End: 521.8 Briefing duration unchanged -> notes 'figure at 08:40' still point to the (now silent) moment.
Remove an off-record aside without trimming
A short off-record remark sits mid-recording. Trimming it would shift everything after; muting keeps the timeline.
Range: Start: 402.0 End: 409.5 Aside is silent; later content keeps its original timestamps. (Use audio-trimmer instead only if you want it shortened.)
Two sensitive segments in one meeting
A password early on and a client name later. Add both ranges; they are silenced together.
Add range 1 -> Start: 95.0 End: 97.2 (password) Add range 2 -> Start: 760.4 End: 762.0 (client name) Both windows muted in a single pass; order doesn't matter.
Tighten an over-wide range
First pass muted 5 seconds but only 2 needed silencing, cutting useful context. Narrow the range and re-run from the source.
Before: Start: 300.0 End: 305.0 (too wide) After: Start: 301.5 End: 303.4 (just the phrase) Reprocess from the original - non-destructive, no quality stacking.
Edge cases and what actually happens
No range added before processing
RejectedProcessing with zero ranges throws Add at least one redaction range. Add at least one Start/End pair first.
Range muted slightly too much context
ExpectedOver-wide ranges silence useful audio around the sensitive phrase. Narrow Start/End and reprocess from the original file; the source is never altered.
Sensitive word's onset clipped
ExpectedIf Start lands just after the word begins, the first consonant survives. Move Start back 0.2–0.3 s so the full utterance is inside the window.
Inverted range (End before Start)
By designAn empty between window silences nothing; the sensitive content stays audible. Verify End is greater than Start.
Wanting the segment removed, not silenced
Use another toolThis tool mutes in place and keeps length. To physically cut the span, use audio-trimmer or audio-splitter — but note that shortens the file and shifts later timestamps.
Overlapping sensitive ranges
SupportedOverlaps are allowed; the union of the ranges is silenced with no error.
Sensitive detail also in the filename or tags
Not handled hereMuting audio does not change the filename or ID3 tags. Rename the file and use id3-editor for embedded fields.
Recording exceeds tier duration
RejectedDuration is capped per tier (Free 30 min, Pro 120 min, higher tiers unlimited) independently of file size.
Lossy input re-encoded on output
ExpectedAn MP3/M4A/OGG/Opus output is re-compressed once. Use WAV/FLAC output to keep the kept audio lossless.
Frequently asked questions
Will the redacted file be the same length as the original?
Yes. Muting a range does not remove time — the silenced spans stay in place, so the total duration is unchanged. This is intentional: it keeps every later timestamp aligned with your notes, transcript, or video. If you actually want the file shorter, trim or strip silence instead.
Does the tool insert a beep, tone, or white noise over the redacted part?
No. The redactor sets the volume to 0 inside each range, so the segment becomes full silence. There is no beep tone, 1 kHz tone, or white-noise option in the tool — it is a mute, not a bleep. If you specifically need an audible censor beep for broadcast style, you would have to add it in a separate audio editor; this tool's output is silent across the marked ranges.
How is this different from the silence-stripper?
Opposite goals. silence-stripper detects and removes quiet gaps to tighten a recording, shortening it. The PII redactor inserts silence into specific time ranges you choose, keeping the total length identical so timing and any synced transcript line up. Use the redactor when you must blank out content without shifting everything after it.
Should I just trim out the sensitive part instead?
Trimming with audio-trimmer physically cuts a span, which shortens the file and shifts every later timestamp — bad if you have a synced transcript, captions, or chapter markers. Redacting mutes in place and keeps the timeline intact. Trim when the sensitive part is at the very start/end and length doesn't matter; redact when it is mid-recording or timing must be preserved.
Can it automatically find names, numbers, or card details?
No. Marking is manual only — you add ranges and type the Start and End seconds yourself. There is no speech-to-text, entity recognition, or phone-number detector built in. Play the recording, note the timestamps where sensitive content is spoken, and enter those ranges. This keeps everything in the browser with zero upload, but it does mean you (or a reviewer) decide what gets silenced.
How precise can the redaction boundaries be?
The Start and End inputs step in 0.1 s (100 ms) increments, and the underlying between(t, start, end) filter uses the exact number you type. For most speech that 100 ms granularity is enough to catch a spoken digit or word; pad each range by a few hundred milliseconds on both sides so the leading consonant or trailing syllable is fully covered.
How many separate sections can I redact in one pass?
As many as you need — click Add range for each section. Every range is applied in the same processing pass as its own volume=0 gate, so a call with ten scattered account numbers is one job, not ten. There is no fixed cap on range count; the practical limits are the file-size and duration caps for your tier.
What happens if two ranges overlap?
Overlapping ranges are fine — each is an independent volume=0 gate, so the union of all ranges is silenced. If range A is 10–15 s and range B is 14–20 s, the audio from 10–20 s ends up silent. There is no error for overlap; it simply mutes everything any range covers.
Can the silenced audio be recovered from the output file?
No. The samples inside each range are replaced with silence before encoding, so the original audio in those spans is not present in the output file — there is nothing to un-mute. Keep your original recording in a secure location if you ever need the un-redacted version; the redacted file cannot be reversed back to it.
Is my recording uploaded to a server?
No. All processing is 100% in your browser using FFmpeg 8.1 compiled to WebAssembly. The audio is decoded and redacted locally and never transmitted, which is what makes the tool suitable for sensitive recordings. You can disconnect from the network after the page loads and redaction still works.
Does redacting also remove names or numbers stored in the file's metadata?
No. This tool silences audio samples within the ranges you mark; it does not touch ID3 tags, comments, or cover art embedded in the file. If a phone number or name is sitting in the title/artist/comment fields, edit those separately with id3-editor, and consider whether the filename itself leaks anything.
Does the output stay in the same format as my input?
By default yes — the output extension follows the input file's extension and is re-encoded with the matching encoder (MP3 to libmp3lame, WAV to pcm_s16le, FLAC to flac, M4A to aac, OGG to libvorbis, Opus to libopus). So an MP3 in gives an MP3 out, named with a -redacted suffix.
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.