Turn Opus files into M4A
Your Opus goes in and an M4A comes out. M4A is the audio file Apple software produces, carrying a track along with its artwork, title and chapters. Your file never leaves your computer.
Need the other direction? Convert M4A to Opus
How to convert Opus to M4A
- 1 Drop your Opus .opus file onto the page, or click to browse for it.
- 2 Set the quality, or leave the default, which keeps the file small without anything showing.
- 3 Convert. The work happens on your own machine, so how long it takes depends on your computer and the file.
- 4 Download the M4A, or add more files and do the whole set in one go.
Why convert Opus to M4A
- Holds the title, the artwork and the chapters properly.
- Can hold a lossless track as well as a compressed one.
- Voice memos recorded on Apple devices.
- Opus: car stereos and standalone players mostly will not open it.
Opus compared with M4A
How the two formats differ on the things that decide whether a conversion is worth making.
| Property | Opus | M4A |
|---|---|---|
| File extension | .opus | .m4a |
| Compression | Lossy | Lossy or lossless |
| Typical file size | Smaller | Depends on mode |
| Browser support | All current browsers | Every browser |
| Introduced | 2012 | 2001 |
| Developed by | Xiph.Org and IETF | Apple / ISO |
Quality and what changes
M4A stores the same content under a different set of rules, so what matters here is compatibility rather than picture quality. Convert once from the best source you have rather than through a chain of intermediate files.
- One M4A limitation to keep in mind: the extension does not tell you what is actually inside.
Questions about Opus to M4A
Is my Opus file uploaded anywhere?
No. The whole thing runs inside the browser tab you already have open. Your Opus is read straight from your own disk, converted on your machine and handed back as an M4A. Nothing is sent anywhere, nothing is stored and there is no account.
Is there a file size limit?
There is no server-side limit because no server sees the file. The real ceiling is your device memory, since the input and the output both have to fit in the tab. A few hundred megabytes is usually fine on a desktop machine and considerably less on a phone.
Can I convert several Opus files at once?
Yes. Add as many as you like and they are processed one after another, then offered as separate M4A downloads or as a single ZIP. Speed depends on your own processor rather than on a queue.
Does the converter work offline?
Yes, after the page has loaded once. The engine is cached by the browser, so you can disconnect, reload and keep converting. That falls out of doing the work locally rather than being a separate mode you switch on.