How to reduce audio file size without uploading
- Step 1Open the page (optionally then go offline) — Load this tool while online so the FFmpeg WebAssembly engine downloads. If you want to verify nothing is sent, disconnect your network now — compression still works because the engine is already in your browser.
- Step 2Drop the sensitive recording — Drag the MP3, WAV, M4A, OGG, Opus, FLAC or video file onto the dropzone. It's read into the tab's memory locally — there is no upload step and no progress bar, because no bytes are being transmitted.
- Step 3Set the target size — Enter your target in Target size (MB). Whatever you need to email a redacted copy, attach to a case file, or store compactly — the field accepts 0.5 to 500 MB in 0.5 MB steps.
- Step 4Run the reduction locally — Click Run Compress to Size. FFmpeg 8.1 re-encodes to a CBR MP3 entirely in your browser. The result card reports input and output bytes and encode time — all computed on your machine.
- Step 5Verify the size, then download — Check the Output size meets your target, audition in the inline player if needed, then press Download. The file saves directly to your device as
name-Nmb.mp3— no cloud step, no link generation. - Step 6Clear the tab when finished — Closing or refreshing the tab discards the in-memory copy of the recording. Nothing persists server-side; the only record is your downloaded file and any local browser cache of the engine itself.
In-browser (this tool) vs. upload-based compressors
Why local processing matters for confidential audio. JAD's audio tools never transmit the file.
| Aspect | This tool (in-browser) | Typical upload compressor |
|---|---|---|
| File leaves device | Never | Yes — uploaded to a server |
| Server-side copy | None | Held during (and sometimes after) processing |
| Works offline | Yes, after page load | No — needs the round trip |
| Retention/log risk | None (no file arrives) | Depends on their policy |
| Account required | No (free tier) | Often yes |
| Result delivery | Direct download | Download link / cloud |
What stays on your device
Exactly what is and isn't local when you use this tool.
| Item | Where it lives | Detail |
|---|---|---|
| Source recording | Browser memory only | Read locally; never transmitted |
| FFmpeg engine | Browser cache | WebAssembly module, fetched once |
| Compressed output | Your downloads | Saved directly, no upload of result |
| Usage counter | Account stats (if signed in) | A count only — no file content |
Tier limits for this tool
Audio family limits from JAD's tier configuration. Free covers most confidential clips without an account.
| Tier | Max file size | Max duration | 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
Confidential-workflow scenarios where keeping the recording off any server is the requirement, not a nicety.
Compress an interview recording under NDA
A journalist's source interview must not touch a third-party server. In-browser processing means it never does.
Source: source-interview.wav · 28 min · 47 MB (PCM) Target: 20 MB (to archive compactly) Processing: 100% local (FFmpeg WASM in your browser) Network: no upload request for the file at any point Output: source-interview-20mb.mp3 · ~19 MB · 96 kbps The recording never left the laptop.
Shrink a legal deposition clip for a case file
Legal audio often can't be uploaded to consumer services. Local sizing produces a court-attachable MP3 without exposure.
Source: deposition-clip.m4a · 12 min · 18 MB (AAC) Target: 8 MB (case-management upload cap) Processing: local only Output: deposition-clip-8mb.mp3 · ~7.0 MB · 80 kbps Voice fully intelligible for the record; no server copy.
Verify privacy by going offline first
You can prove nothing is transmitted: load the page, disconnect, then process. It still works.
1. Open the tool while online (engine loads) 2. Disconnect Wi-Fi / unplug ethernet 3. Drop the recording, set target, Run 4. Compression completes offline → download No network = no upload. Reconnect afterward if you like.
Compress a medical dictation locally
Patient-identifiable audio shouldn't be uploaded to a random web tool. In-browser keeps it compliant with your own handling rules.
Source: dictation.wav · 9 min · 15 MB (PCM) Target: 5 MB Processing: local only — no PHI transmitted Output: dictation-5mb.mp3 · ~4.7 MB · 64 kbps Keep on the secured device; nothing was sent off it.
Redact first, then size — both stay local
Mute sensitive segments before sizing. The redactor also runs in-browser, so the whole chain is upload-free.
Step 1: /audio-tools/pii-redactor → mute name/SSN ranges Step 2: this tool, Target 8 MB → sized redacted copy Both steps run locally via FFmpeg WASM. Output: redacted-8mb.mp3 — safe to share, never uploaded.
Edge cases and what actually happens
Confirming nothing is uploaded
VerifiableYou don't have to take it on faith. Open the page online so the engine loads, then disconnect your network and run the compression — it completes offline, which is only possible because the file is processed locally. You can also watch the browser's network panel: no request carries the audio bytes.
Engine download requires a connection
ExpectedThe FFmpeg WebAssembly module itself must be fetched the first time you load the page (it's then cached). That fetch is the engine code, not your file. After it's cached, you can process subsequent files offline. Your audio is never part of any request.
Usage counter for signed-in users
PreservedIf you're signed in, JAD increments a usage count for dashboard stats. This is a number only — no file name, no content, no audio. Free tier needs no account at all, so even that counter is optional for confidential one-off jobs.
Large confidential file over the free cap
Tier limitFree tier processes up to 50 MB / 30 minutes locally. A longer recording is blocked before processing — but note the block is local too; nothing was uploaded to determine it. Pro (200 MB / 120 min) and Pro + Media (100 GB) raise the cap, still processing entirely in-browser.
Downloaded copy is your responsibility
By designThe tool never uploads, but the compressed file you download is a real copy on your disk. Store it on your secured device per your own handling rules. Where you send it afterward (email, case system) is outside the tool's privacy boundary.
Browser cache holds the engine, not your audio
By designYour browser caches the WebAssembly engine for speed. It does not cache your recording — the in-memory copy is discarded when you close or refresh the tab. Clearing site data removes the cached engine but there was never an audio file stored to remove.
Output format is MP3 in the browser
By designThe in-browser tool outputs MP3, which gives predictable size-per-bitrate behaviour. The processor/API can emit WAV/FLAC/M4A/OGG/Opus via the format option through the local @jadapps/runner — also fully local, no upload. For an exact MB target, MP3 is the right choice.
You needed encryption, not just no-upload
Out of scopeThis tool guarantees the file isn't uploaded; it does not encrypt the output. The downloaded MP3 is a plain file on your disk. If your workflow requires encryption at rest, apply it separately (e.g. an encrypted volume) after downloading.
Frequently asked questions
Is my recording really not uploaded?
Correct — it is never uploaded. All processing runs in your browser via FFmpeg 8.1 compiled to WebAssembly. The audio is read into the tab's memory and re-encoded locally; no network request carries the file. You can verify by disconnecting your network after the page loads and confirming compression still works.
How can processing work without uploading?
Modern browsers run a full FFmpeg build compiled to WebAssembly directly on your machine. The decode and encode happen on your CPU, in the tab, exactly as a desktop app would — just without installing anything. The server only ever sent you the engine code, never received your file.
Can I use this for confidential or NDA-bound audio?
Yes — that's the primary use case. Because the file never leaves your device, there's no third-party copy to retain or expose. Note that you're still responsible for the downloaded file and wherever you send it afterward; the no-upload guarantee covers the compression step itself.
Does it work offline?
After the page loads (which downloads the engine), yes. You can disconnect the network and compress — proof that nothing is transmitted. The only thing that needs a connection is the initial one-time engine fetch, which is cached afterward.
What about the usage counter — does that send my file?
No. If you're signed in, JAD increments a count for dashboard stats — a number only, with no file name or content. The free tier requires no account at all, so for a one-off confidential job there's no counter and no sign-in trail.
How do I reduce the size without uploading?
Drop the file, set Target size (MB), and run. JAD computes the bitrate from the clip's duration and snaps down to a standard MP3 rate so the output meets your target — all locally. Download saves directly to your device with a -Nmb.mp3 suffix.
Is the output encrypted?
No — the tool guarantees no upload, not encryption. The downloaded MP3 is a normal file on your disk. If you need encryption at rest, apply it yourself (e.g. store the file in an encrypted volume) after downloading.
Can I redact sensitive parts before compressing?
Yes, and it stays local. Use PII Redactor to mute specific time ranges first, then size the redacted copy here. Both tools run in-browser via FFmpeg WASM, so the whole chain is upload-free.
How big a confidential file can I process for free?
Up to 50 MB and 30 minutes on the free tier, with no account. Larger or longer files need Pro (200 MB / 120 min) or Pro + Media (100 GB, no duration cap) — and those still process entirely in your browser with no upload.
Does compressing change the audio content?
Only its bitrate, to meet the size — it does not edit, censor, or alter the spoken content. To remove sensitive segments, use PII Redactor before sizing. To change loudness, use Loudness Normalizer.
What output formats are available?
The browser tool outputs MP3 (best for hitting a size target). WAV, FLAC, M4A, OGG and Opus are available via the local @jadapps/runner using the format option — which also runs entirely on your machine with no upload.
Can I batch-process confidential files locally?
Yes. The @jadapps/runner processes files on your machine — POST each to the local audio-compressor endpoint with a targetMb. Nothing uploads. Pro's in-browser batch (10 files) is another fully-local option for sizing several at once.
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.