AMR to F4B Converter
Processing entirely on your device — large files may take a moment.
AMR is the tiny voice-recording format of old Nokia-era phones and answering machines. Convert F4B audiobooks exactly like M4B — to MP3, M4A or WAV.
iLoveConverter processes everything locally on your computer, which makes it private and fast: no upload wait, no server storage, no limits. Add as many files as you like — batch conversion is built in.
How AMR compares to F4B
| AMR | F4B | |
|---|---|---|
| Compression | Lossy speech codec | Lossy AAC + chapters |
| Quality | Speech only | Speech-optimized bitrates |
| Compatibility | Phone recorders | Apple Books, Audible |
| Best for | Voice memos and call recordings | Chaptered audiobooks |
How to convert AMR to F4B
- 1
Select your files
Drag & drop your AMR 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 AMR format
AMR (Adaptive Multi-Rate) is the speech codec of 2G/3G telephony, and the default recording format of countless feature phones and early smartphones. It is optimized exclusively for human voice: narrowband (300–3400 Hz) and wideband (AMR-WB, 50–7000 Hz) modes that make calls sound like calls.
For voice memos it is remarkably compact — a few kilobits per second. For anything musical it is hopeless: cymbals, bass and anything above its band simply do not exist. Convert AMR voice notes to MP3/Opus for archiving and playback anywhere else.
+Strengths
- ✓Extremely compact for speech
- ✓Native phone-recorder format
!Limitations
- −Voice-only: music quality is unusable
- −Narrow bandwidth sounds dated
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 AMR to F4B?
There is a concrete reason this conversion exists: Voice-only: music quality is unusable F4B 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 AMR 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 AMR 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.
Can I convert a whole folder of AMR 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 AMR to F4B reduce audio quality?
If F4B is lossless, the output contains everything the AMR 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.