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OPUS to M4A converter

Convert OPUS to M4A in your browser. No upload and no account: the file never leaves your device, so the only size limit is your device’s memory.

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Related conversions

Need it the other way round? Convert M4A to OPUS

Other ways to convert OPUS

Convert other formats to M4A

Read more about the OPUS format and the M4A format, or see every audio tool and all audio conversions.

Should you convert OPUS to M4A?

You want voice notes in a format iPhones and Macs play natively.

Fine when a player or app needs M4A. Converting between two lossy formats compresses the sound a second time, so match or exceed the original bitrate to keep the loss inaudible.

M4A also plays in more places: Apple devices, Android, browsers and most players; some older car stereos, Windows apps and forms refuse it.

OPUS is the most efficient audio codec in common use, especially for speech; M4A is AAC audio in an MP4 container, Apple’s everyday audio format. Use M4A for music and recordings on Apple devices, or anywhere AAC is accepted and size matters.

OPUS and M4A compared
Property OPUS M4A
Compression Lossy Lossy
Typical quality 24–128 kbps 128–256 kbps AAC
Support Has patchy support Opens almost everywhere
Best for Voice notes, calls and streaming at low bitrates Good-sounding audio at small sizes
Introduced 2012 2003

How to convert OPUS to M4A

  1. 01

    Add your OPUS

    Drop your OPUS file onto the box, or click to choose it. It is read from your disk and stays there.

  2. 02

    Check the settings

    The output is already set to M4A. Change the bitrate if you want to; the defaults suit most files.

  3. 03

    Save the M4A

    Press convert and save the M4A. Several files come back together as a ZIP.

What changes when OPUS becomes M4A

Two rounds of compression

Each lossy encode throws away a little more. A OPUS at 128 kbps converted to M4A at 192 kbps sounds like the original; converted at 96 kbps it can turn swirly and dull.

Expect a larger file

M4A generally takes more room than OPUS. If the file has to fit an upload limit, check the size once it’s converted. OPUS: A minute of voice note is often under 200 KB. M4A: About 1 MB a minute at 128 kbps.

This page is put together from our notes on each format, choosing only what is true of OPUS and M4A, so every pairing states the same facts the same way. How these pages are made.

Why it doesn’t upload

Recordings are often private: interviews, voice notes, unreleased music. Your browser can decode and encode audio itself, so there is no reason to send it anywhere.

How to check for yourself

Worth knowing

  • About the OPUS. WhatsApp voice notes exported from a phone are Opus files, sometimes named .ogg, which many players and transcription services refuse.
  • About the M4A. An .m4a can also hold lossless ALAC audio, several times larger; the extension alone doesn’t tell you which.
  • MP3, WAV, M4A, OGG, Opus and FLAC are converted by your browser directly. WMA, AMR, APE, AC3 and the other specialist formats use the FFmpeg engine, a one-time 31 MB download.

Questions

Does converting OPUS to M4A lose quality?

M4A is lossy, so a little is discarded, but at the default bitrate the difference is inaudible for nearly everyone.

Will an M4A play in my car or on my phone?

M4A opens almost everywhere: Apple devices, Android, browsers and most players; some older car stereos, Windows apps and forms refuse it.

Read more about this

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