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M4A to OPUS converter

Convert M4A to OPUS 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 OPUS to M4A

Other ways to convert M4A

Convert other formats to OPUS

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

Should you convert M4A to OPUS?

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

M4A is AAC audio in an MP4 container, Apple’s everyday audio format; OPUS is the most efficient audio codec in common use, especially for speech. Use Opus for speech and streaming where small size matters more than compatibility.

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

How to convert M4A to OPUS

  1. 01

    Add your M4A

    Drop your M4A 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 OPUS. Change the bitrate if you want to; the defaults suit most files.

  3. 03

    Save the OPUS

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

What changes when M4A becomes OPUS

Two rounds of compression

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

Opus runs at 48 kHz

Opus always works at 48 kHz internally, so other sample rates are converted. It sounds excellent at low bitrates, especially for voice.

Expect a smaller file

OPUS usually stores the same content in less space than M4A. M4A: About 1 MB a minute at 128 kbps. OPUS: A minute of voice note is often under 200 KB.

This page is put together from our notes on each format, choosing only what is true of M4A and OPUS, 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 M4A. An .m4a can also hold lossless ALAC audio, several times larger; the extension alone doesn’t tell you which.
  • About the OPUS. WhatsApp voice notes exported from a phone are Opus files, sometimes named .ogg, which many players and transcription services refuse.
  • 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 M4A to OPUS lose quality?

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

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

OPUS has patchy support: browsers, Android and chat apps; many media players, editors and forms can’t open .opus files.

Read more about this

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