AMR to M4B Converter
Processing entirely on your device — large files may take a moment.
Adaptive Multi-Rate Audio and MPEG-4 Audiobook exist for different jobs: AMR is the tiny voice-recording format of old Nokia-era phones and answering machines. 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 AMR compares to M4B
| AMR | M4B | |
|---|---|---|
| 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 M4B
- 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 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 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 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 AMR to M4B?
Converting makes sense where the strengths of M4B meet what AMR cannot give you. Chapter markers survive on Apple platforms Meanwhile Voice-only: music quality is unusable One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this AMR 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 AMR 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 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.
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.