Convert Opus to M4A online

Your Opus file is converted to M4A right here in your browser, using FFmpeg compiled to WebAssembly. Nothing is uploaded to us, the audio never leaves your device. Quality is preserved and the download is ready in seconds.

What is an Opus file?

Opus is the newest major audio codec (standardised in 2012) and the best-in-class at speech and low bitrates. Which is exactly why WhatsApp voice notes are Opus files. It was designed for real-time internet audio and it is what Discord, WhatsApp and most VoIP apps use.

Every WhatsApp voice note you have ever received is an Opus file. Discord recordings, Telegram voice messages and browser-based calls use it too. So 'a.opus file I can't open' is one of the most common conversion needs in Nigeria.

Why M4A?

M4A is the MPEG-4 audio container, almost always holding AAC-encoded audio. It is what an iPhone produces: Voice Memos, iTunes purchases and most Apple-ecosystem audio are M4A files.

Convert to M4A for the Apple ecosystem, or when you want noticeably better quality than MP3 at the same file size, AAC is MP3's designed successor and it shows at lower bitrates. Opus support outside chat apps is patchy: many car stereos, editors and upload forms don't accept it, which is why voice notes so often need converting to MP3 or WAV first.

Frequently asked questions

Will converting Opus to M4A lose quality?

A small, one-time generational loss is unavoidable. Both Opus and M4A are lossy, so re-encoding discards a little more detail. The converter uses high-quality settings to keep it inaudible for speech, but if you still have the original uncompressed source, converting from that instead is always better.

Is it free?

Yes, completely, with no account and no watermark. The conversion runs on your own device, so it costs us nothing to let you use it. The only limit is file size: up to 50 MB, which is what a browser can hold in memory comfortably.

Do I need to install anything, or upload my file?

Neither. It runs entirely in your browser using FFmpeg compiled to WebAssembly. Your audio is never sent to us, which is also why it works on a slow connection, only the page downloads, not your file.

Need a transcript of the audio?

Autrans also transcribes audio in Nigerian English, Pidgin, Yoruba, Hausa, Igbo, French, and Spanish.