Opus to M4A Converter — Free, Online, No Upload

Opus is the codec inside Discord voice messages, WhatsApp voice notes, Telegram audio, and most WebRTC recordings. It's technically excellent — low latency, efficient compression, widely supported in browsers. But iOS's Music app won't play it, iTunes won't import it, and the native Apple audio stack treats Opus files as unrecognised. When someone sends you a voice note or a Discord bot exports audio and you want to listen to it properly on your Apple devices, Opus is a dead end without conversion.

M4A is Apple's native container for AAC audio and is natively supported by every Apple device made in the last 15 years. Converting Opus to M4A makes the audio playable in the iPhone's native Music app, importable into iTunes, syncable to Apple Watch, and streamable over AirPlay. The conversion involves re-encoding the audio — Opus is decoded and then re-encoded as AAC inside an M4A container — which introduces a small quality reduction inherent to transcoding between lossy codecs.

This converter writes the M4A at 192 kbps to keep that impact small. At 192 kbps, the difference from the Opus source is negligible in normal listening conditions. The file size will increase compared to the Opus source because AAC is less efficient than Opus at the same perceived quality level — a trade-off for the broad Apple ecosystem compatibility the M4A format provides.

Typical sizes (3-minute song): OPUS 1–3 MB → M4A 3–6 MB.

M4A output is encoded at 192 kbps.

Re-encoding one lossy format into another adds a second round of compression.