Convert M4A files to OPUS free in your browser — no signup, no install, and the file is never uploaded to a server. OPUS compresses further, so the file gets noticeably smaller.
Add your M4A file
Drag the M4A file onto the drop area above, or click it to pick a file from your device. You can add several files at once.
Confirm OPUS as the output
OPUS is already selected as the output format on this page. You can pick the bitrate — higher keeps more of the sound, lower makes a smaller file.
Run the conversion
Press the convert button. Audio decodes and re-encodes in your browser — a normal song finishes in a few seconds.
Download the OPUS file
When it finishes, download the OPUS file. Converting multiple files gives you the option to download them together as a ZIP.
An audio file in an MPEG-4 container, usually compressed with AAC. iPhone voice memos and iTunes purchases use this format.
A modern codec offering the best efficiency available today for both speech and music. Discord, WhatsApp, and other real-time voice services use it.
Yes. M4A to OPUS conversion is completely free with no signup, no watermark, and no daily limit on the free plan for ordinary use.
No. The conversion runs entirely inside your browser using WebAssembly, so the M4A file never leaves your device. That is also why it works without an internet connection once the page has loaded.
OPUS uses lossy compression, so some detail is discarded. At high quality settings the difference is usually invisible, and the file becomes far smaller.
OPUS is a newer format. Current browsers and phones handle it, but older desktop software may not — keep the original M4A if you have to send it to someone on an old machine.
The free plan handles files up to 200MB. Because processing happens on your own device, very large files depend on your computer's memory rather than a server quota.
Audio converter
What each file format is, what it is used for, and which formats it can be converted to.
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