M4B to ALAC Converter
Convert M4B files to ALAC format online for free. No installation or registration required.
Quick Answer: How to Convert M4B to ALAC
M4B is an audiobook-profile MP4 audio file with chapter markers and bookmarking, while ALAC is Apple Lossless — FLAC's counterpart inside the MP4/M4A container. Converting M4B to ALAC wraps or re-encodes your audio into the ALAC structure, but be aware: quality lost when the M4B was created stays lost — a ALAC made from a lossy source is a perfect copy of an imperfect original. Run it free at practicalwebtools.com/convert/audio/m4b-to-alac: drop in your M4B, adjust settings if you like, and download the ALAC — no signup, no upload, everything stays on your device.
M4B vs ALAC: Which One and Why
M4B is an audiobook-profile MP4 audio file with chapter markers and bookmarking, Apple's audiobook extension of M4A (iTunes era, mid-2000s). ALAC is Apple Lossless — FLAC's counterpart inside the MP4/M4A container, released by Apple in 2004; open-sourced under Apache 2.0 in 2011. People reach for M4B mainly for audiobooks, long-form podcasts with chapters, while ALAC is the usual choice for Apple Music lossless streaming, ripping CDs for the Apple ecosystem, iPhone/local-library audiophile setups. M4B's headline strength: iOS/Apple Books remember your playback position per file. ALAC's: perfect fidelity inside the iTunes/Apple Music pipeline. On the other side of the ledger, M4B limitation: playback support outside Apple Books and audiobook apps is spotty — and ALAC limitation: no advantage over FLAC outside the Apple world.
How to Convert M4B to ALAC Online
- 1
Add your M4B file: Drag and drop it into the converter, or click to browse. M4B files up to the size limit are accepted, and nothing is uploaded — processing runs locally in your browser.
- 2
Set ALAC options: The converter re-encodes into ALAC, which is lossless — roughly 40–60% of original size, comparable to FLAC. Set quality to maximum since you're going lossless — no reason to trim bits you already have.
- 3
Download the ALAC: Conversion runs on your device. When it completes, download the ALAC file — repeat for as many files as you need, free and unlimited.
Key Facts
- M4B: Apple's audiobook extension of M4A (iTunes era, mid-2000s), AAC (usually) inside an MP4 container.
- ALAC: released by Apple in 2004; open-sourced under Apache 2.0 in 2011, lossless — roughly 40–60% of original size, comparable to FLAC.
- Converting M4B → ALAC cannot restore what the M4B encoding already discarded — the ALAC is a faithful copy of the M4B, not of the original recording.
- M4B strength: iOS/Apple Books remember your playback position per file.
- ALAC strength: perfect fidelity inside the iTunes/Apple Music pipeline.
- M4B limitation to know: playback support outside Apple Books and audiobook apps is spotty.
- ALAC limitation to know: no advantage over FLAC outside the Apple world.
- Fun fact: Apple Music streams ALAC up to 24-bit/192 kHz — but AirPods re-compress it to AAC over Bluetooth, so lossless is only audible on wired or Wi-Fi playback
Format Background
M4B
M4B — Apple's audiobook extension of M4A (iTunes era, mid-2000s). the "bookmark" behavior comes from an iTunes metadata flag (`stik` = 2, "audiobook"), not from any difference in the audio stream
ALAC
ALAC — released by Apple in 2004; open-sourced under Apache 2.0 in 2011. Apple Music streams ALAC up to 24-bit/192 kHz — but AirPods re-compress it to AAC over Bluetooth, so lossless is only audible on wired or Wi-Fi playback
Frequently Asked Questions
Will converting M4B to ALAC lose quality?
The ALAC output preserves everything present in your M4B file — but M4B is AAC (usually) inside an MP4 container, so information discarded when that file was made is gone for good. You get a bit-perfect copy of what you have, not a restoration of the original recording.
Are my files uploaded anywhere during M4B → ALAC conversion?
No. This converter runs on WebAssembly inside your browser — your M4B file is read from disk, processed by your device's CPU, and the ALAC is written back locally. There is no server upload at any point, which also means no size-based throttling or waiting in queue.
Does converting M4B to ALAC restore lost quality?
No — and this trips up a lot of people. M4B is AAC (usually) inside an MP4 container: the data it discarded at creation time cannot be reconstructed by any converter. A ALAC from a M4B source sounds exactly as good as the M4B, no better. The reasons to convert anyway are compatibility, editing headroom, and future-proofing — not restoration.
What devices and apps play ALAC files?
iOS, macOS, iTunes, Apple TV, HomePod; most modern browsers via MSE. No advantage over FLAC outside the Apple world — worth knowing before you standardize on it.
Can I convert several M4B files at once?
Yes — the converter processes a queue of files in one session, each entirely on your device. Batch mode is handy when moving a library into ALAC; just remember each file re-encodes independently, so set your quality once and it applies to all.
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Further reading
Guides and explainers on the Practical Web Tools blog cover audio and video formats in depth — or browse every audio converters pair from the hub.