M4R to M4B Converter
Processing entirely on your device — large files may take a moment.
M4R is Apple’s ringtone format — technically an AAC file capped at 40 seconds that iTunes and iPhones recognise as a ringtone. Converting M4B to MP3 frees audiobooks to play on car stereos, dumb players and anything without chapter support.
Because the whole conversion happens on your device, it is instant, unlimited and genuinely private — no accounts, no watermarks, no files on anyone's server. Multiple files are converted in one go.
How M4R compares to M4B
| M4R | M4B | |
|---|---|---|
| Compression | Lossy AAC | Lossy AAC + chapters |
| Quality | Same as M4A | Speech-optimized bitrates |
| Compatibility | iPhone only | Apple Books, Audible |
| Best for | iPhone ringtones | Chaptered audiobooks |
How to convert M4R to M4B
- 1
Select your files
Drag & drop your M4R files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to M4B". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted M4B file individually, or grab everything at once as a ZIP archive.
About the M4R format
M4R is simply iPhone ringtone packaging: an AAC audio file (same as M4A) capped at 40 seconds, named .m4r so iOS treats it as a ringtone instead of a song. GarageBand and Finder sync are the supported paths to install one; the audio itself is ordinary AAC.
Practical workflow: pick the 30–40 second chorus you want, convert to M4R, sync it to the phone, and set it in Sounds & Haptics. Nothing about the audio changes — the extension and the length limit are the entire format.
+ Strengths
- ✓The native iPhone ringtone format
- ✓Simple — it is AAC with a new name
! Limitations
- −Hard 40-second length cap
- −Installation requires sync or GarageBand
About the M4B format
M4B is M4A wearing an audiobook badge: the same AAC audio in an MP4 container, plus chapter markers that Apple Books and Audible apps render as a scrubbing timeline. Buy an audiobook outside Audible and it likely arrives as M4B.
The format is deliberately chained to Apple's book ecosystem. Converting M4B to MP3 sets the book free: car stereos, gym players, old iPods and every app without chapter support will play it — though the chapter marks themselves are flattened away.
+ Strengths
- ✓Chapter markers survive on Apple platforms
- ✓Efficient AAC audio
! Limitations
- −Chapters vanish in MP3 conversion
- −Non-Apple support is patchy
Why convert M4R to M4B?
There is a concrete reason this conversion exists: Hard 40-second length cap M4B sidesteps that — Chapter markers survive on Apple platforms If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this M4R to M4B converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for M4R to M4B?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Can I convert a whole folder of M4R files?
You can select many files at once and they are processed in a single batch. Output files land in one ZIP download when there is more than one result.
Will converting M4R to M4B reduce audio quality?
If M4B is lossless, the output contains everything the M4R file contains — no further loss is added. If M4B is lossy, one recompression pass is unavoidable; the quality slider controls how much. Loss that already happened in the source file can never be undone by converting.