M4R to F4B Converter
Processing entirely on your device — large files may take a moment.
iPhone Ringtone and Adobe Flash Audiobook (F4B) exist for different jobs: M4R is Apple’s ringtone format — technically an AAC file capped at 40 seconds that iTunes and iPhones recognise as a ringtone. Convert F4B audiobooks exactly like M4B — to MP3, M4A or WAV.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How M4R compares to F4B
| M4R | F4B | |
|---|---|---|
| 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 F4B
- 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 F4B". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted F4B 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 F4B 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 F4B?
Converting makes sense where the strengths of F4B meet what M4R cannot give you. Chapter markers survive on Apple platforms Meanwhile Hard 40-second length cap One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this M4R to F4B 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 F4B?
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.
Are tags like title and artist preserved?
Tag handling varies between target formats and this conversion focuses on the audio itself. For archival copies where tags matter, keep the original file; the converted copy is for playback and sharing.
Will converting M4R to F4B reduce audio quality?
If F4B is lossless, the output contains everything the M4R file contains — no further loss is added. If F4B 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.