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Free · in-browser · no uploads

Optimize audio for speech recognition: 16 kHz mono.

Turn any recording into the 16 kHz mono file speech models read, as WAV or a small MP3. Runs in your browser; the file never leaves your device.

16 kHz mono · WAV or MP3 · 50 MB browser cap · No signup
Drop audio here or click to pick a file
MP3, WAV, M4A, AAC, OGG, FLAC, Opus, WebM · up to 50MB
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Drop a file to start. Everything happens in your browser.
Optimized · ready.
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How it works

Three steps. Zero uploads. The entire pipeline runs in your browser tab.

1

Drop the file

Click the drop zone or drag a file in. We read it locally — no network call is made to open it.

2

Resample in your browser

FFmpeg downmixes to mono and resamples to 16 kHz inside a Web Worker via WebAssembly. No server round-trip.

3

Download

Grab the new file with one click. Everything stays local until you choose where it goes.

Frequently asked

What format do speech recognition models want?

Most speech models process 16 kHz mono internally. Converting first removes resampling surprises and cuts file size versus 44.1/48 kHz stereo.

Does 16 kHz mono hurt quality?

Not for speech recognition — speech intelligibility lives below 8 kHz (the Nyquist limit of 16 kHz sampling), which is why telephony and ASR standardized there.

Do I need this before uploading to WhipScribe?

No. WhipScribe converts every recording to 16 kHz mono on its own servers, so upload the original. This tool is for your own speech-recognition experiments, or to make a file small enough to send.

Do my files get uploaded?

No — conversion runs via ffmpeg-wasm in your browser.

Why does it take 10 to 15 seconds the first time?

The first click loads a 32 MB WebAssembly build of FFmpeg. Your browser caches it, so later runs in the same tab start at once.

What is the file size limit?

50 MB per file, because the work happens in your browser's memory. A longer recording does not need this step to be transcribed: WhipScribe takes one file up to 10 hours or 5 GB as it is.

From the blog

Need the transcript too?

Paste your YouTube / podcast / Dropbox URL in Whipscribe — we transcribe and let you chat with the transcript. Free preview of the opening minutes; packs from $4.

Open Whipscribe →

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