Drop a .opus file and it is encoded to MP3 on your device — plays everywhere, nothing uploaded.
Drop a .opus file and it is encoded to MP3 on your device — plays everywhere, nothing uploaded.
Convert Opus audio files to MP3 in your browser. Opus is the modern codec behind WhatsApp and Telegram voice notes, Discord, and browser recordings. It's excellent for speech at low bitrates — and most media players, editors, and transcription services don't accept it. GhostAudio decodes the file and re-encodes it with the LAME MP3 encoder running in ffmpeg compiled to WebAssembly — on your device, with no upload, no signup, and no queue.
MP3 is the lowest-common-denominator audio format: every phone, car stereo, browser, podcast host, and editing app plays it. You pick the bitrate (64, 96, 128, 192, or 320 kbps; 192 is the default) and can fold stereo down to mono for speech, which halves the size again.
How it works
Drag in the .opus file. It opens in the GhostAudio studio with Convert to MP3 pre-selected.
192 kbps is the default and transparent for most listening; 64–96 kbps with Mono is plenty for voice memos and lectures.
ffmpeg encodes it in your browser. Save the MP3, or keep going — trim, compress, or transcribe it in the same tab.
About Opus
Opus is designed for real-time voice and is very efficient at low bitrates. Voice notes are small in Opus; MP3 at 64–96 kbps mono keeps speech clear at a comparable size.
MP3 is lossy — keep your original
Converting to MP3 discards detail the encoder judges inaudible, and converting back never restores it. Share the MP3; keep the original if you might edit it later.
No. Decoding and encoding both run in your browser via ffmpeg.wasm. There is no upload endpoint for the audio tools — you can confirm it in your browser's Network tab.
128 kbps for casual listening, 192 kbps (the default) when quality matters, 320 kbps for the highest MP3 quality. For speech, 64–96 kbps with Mono sounds clean at a fraction of the size.
Yes. Save the voice note (.opus or .ogg) to your device and drop it here. Speech sounds clean at 64 kbps Mono. You can also transcribe it on-device with Transcribe.
One file per pass today. Each conversion takes seconds and nothing re-uploads, because nothing uploads.
WAV to MP3
Encode a huge WAV as an MP3 — 5–10× smaller, sounds the same.
M4A to MP3
Convert iPhone Voice Memos and iTunes audio to play-everywhere MP3.
Compress audio
Re-encode at a lower bitrate — speech shrinks dramatically.
Trim audio
Cut silence or clip a segment on the waveform, locally.
Transcribe audio
Turn recordings into text with on-device AI — nothing uploaded.
Every GhostAudio tool runs entirely in your browser. Your file is never uploaded — there's no upload endpoint to send it to.