M4B to FLAC Converter
Processing entirely on your device — large files may take a moment.
MPEG-4 Audiobook and FLAC Lossless Audio exist for different jobs: M4B is the audiobook flavour of M4A — AAC audio with chapter markers, used by Audible and Apple Books. Convert to FLAC when you want a permanent, lossless archive of your music.
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 M4B compares to FLAC
| M4B | FLAC | |
|---|---|---|
| Compression | Lossy AAC + chapters | Lossless (~50–60% of PCM) |
| Quality | Speech-optimized bitrates | Bit-perfect |
| Compatibility | Apple Books, Audible | Players, Android, hi-res rigs |
| Best for | Chaptered audiobooks | Music collections and archival |
How to convert M4B to FLAC
- 1
Select your files
Drag & drop your M4B 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 FLAC". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted FLAC file individually, or grab everything at once as a ZIP archive.
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
About the FLAC format
FLAC (Free Lossless Audio Codec, Xiph, 2001) compresses audio to roughly 50–60% of its PCM size and restores every bit on playback — a ZIP for music that also carries proper tags, hi-res support up to 32-bit/655 kHz on paper (24-bit/192 kHz in practice) and full open-source pedigree. It is the archive format of digital music collections.
Support followed maturity: every serious player, modern Android (system-level), most cars and streaming purists' devices handle FLAC natively. Apple resisted for years but iOS 11+ plays it, with the caveat that iTunes/Apple Music syncing still prefers ALAC. The price of losslessness is size — about five times MP3 at comparable quality.
+ Strengths
- ✓Bit-perfect lossless with real compression
- ✓Hi-res capable (24-bit/192 kHz)
- ✓Open, unpatented, tag-native
! Limitations
- −~5× the size of lossy formats
- −Apple syncing prefers ALAC
- −Overkill for casual listening
Why convert M4B to FLAC?
Think of it as moving your file to the container that fits the job. Chapters vanish in MP3 conversion FLAC works differently: Bit-perfect lossless with real compression If any of that sounds like your task, run the conversion — it takes seconds and nothing leaves your device.
Frequently asked questions
Is this M4B to FLAC 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 M4B to FLAC?
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.
Will converting M4B to FLAC reduce audio quality?
If FLAC is lossless, the output contains everything the M4B file contains — no further loss is added. If FLAC 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.
Can I convert a whole folder of M4B 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.