Convert Opus to MP3
Opus is the modern royalty-free audio codec - excellent quality per bit, but limited playback outside browsers and modern desktop OSes (see Audio codecs explained for the wider codec map). Wave decodes Opus in your browser through libopus and re-encodes to a portable MP3 that plays on any device that plays sound.
What actually changes
Opus was standardised as IETF RFC 6716 in 2012 by a working group that included Xiph.Org, Skype, Mozilla, and Broadcom, with the goal of covering the full audio bandwidth from narrow-band speech (6 kbps) through music-quality stereo (256 kbps) in a single codec. It's the audio codec of WebRTC (used by Google Meet, Zoom, Discord voice, WhatsApp voice notes, Signal), the default audio for YouTube AV1 downloads, and the streaming target of many modern podcast platforms.
Wave decodes Opus through ffmpeg-wasm's libopus decoder and re-encodes to MP3 at 192 kbps VBR through libmp3lame. Opus is more efficient than MP3 at low bitrates - a 48 kbps Opus file sounds like a 96 kbps MP3 - so the MP3 output at 192 kbps preserves everything audible in a typical Opus source. For voice-content sources at 32 kbps or lower (WhatsApp voice notes, Discord voice recordings), the MP3 preserves the source's full audible range with plenty of bit budget to spare.
The most common Opus files people convert to MP3 are voice-note archives (WhatsApp, Discord, Signal all default to Opus) and YouTube audio downloads via yt-dlp (which selects Opus-in-WebM for high-quality audio streams). WhatsApp's desktop export writes .opus voice-note files; Discord's message-download feature includes .opus for voice messages; yt-dlp's "-x --audio-format opus" flag produces standalone .opus files. All of them decode cleanly through Wave.
The reason to convert to MP3 is portability. Opus playback is native on modern browsers, macOS 10.13+ (2017), Windows 10+ (2019), and Android 5+ (2014). Older systems, most consumer hardware media players, car head units before ~2020, and voice assistants outside their specific ecosystems don't decode Opus reliably. MP3 plays on all of them. When the goal is "this needs to play on any device I hand it to," the MP3 is the safe target.
Three steps.
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Step 1
Drop the .opus file onto the card.
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Step 2
Wave inspects the source and confirms Decode-and-re-encode.
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Step 3
Convert. Save the MP3.
Answers, specifically.
WhatsApp voice notes as .opus?
Yes. WhatsApp's desktop export writes voice notes as .opus files (usually 24 kbps mono). Wave decodes them cleanly; the MP3 preserves every audible sample.
Discord voice recordings?
Yes. Discord's message-download flow produces .opus files. Wave handles them.
yt-dlp Opus audio extraction?
Yes. yt-dlp's "-x --audio-format opus" writes standalone .opus files from YouTube audio streams. Wave converts them to portable MP3.
Signal voice notes?
Signal encrypts everything at rest, so exports depend on your platform. Where an .opus file is produced (some Android export flows), Wave handles it.
Opus vs MP3 - does the MP3 sound worse?
At the bitrates typical Opus sources use (24-96 kbps for voice, 128-192 kbps for music), the MP3 output at 192 kbps VBR is transparent - the same as or better than the source, plus much better compatibility.
Multi-channel Opus?
Downmixed to stereo before the MP3 encode. Opus's channel-mapping headers describe the layout; Wave uses standard SMPTE fold coefficients.
Opus-in-Ogg vs Opus-in-WebM?
Both work. Standalone .opus is Opus-in-Ogg by convention; the codec inside is the same either way. yt-dlp's WebM output also decodes through the video-source path (see AV1 to MP3 for context).