M4B → M4A
Convert M4B audio to M4A entirely in your browser — no upload, no watermark, no sign-up.
Drop files here
or browse from your device
images · audio · video · documents · archives · up to ~500MB
Your first conversion lands here automatically — saved on this device only, never uploaded.
100% Private
Runs in your browser. No upload.
Instant
No queue, no server roundtrip.
Offline-ready
Works after first load.
Moving M4B audio to M4A is about compatibility and size — which players accept the file and how much disk or bandwidth it costs once it gets there. M4A (MPEG-4 Audio) earns its place here: better sound than MP3 at the same bitrate, with clean chapter and metadata support. M4B is an MP4 audio file flagged as an audiobook, so players remember your position and honour chapter marks. Apple Books and most audiobook apps expect it.
M4B is an MP4 audio file flagged as an audiobook, so players remember your position and honour chapter marks. Apple Books and most audiobook apps expect it.
The audio is decoded and re-encoded, so the running time, channels and sample content stay intact while bitrate and file size follow M4A. Going from a compressed M4B file to any other lossy format is a second generation of compression — start from the highest-quality source you have when it matters, and expect a lossless target to grow the file rather than improve the sound.
What you gain with M4A: Better sound than MP3 at the same bitrate, with clean chapter and metadata support.
Drop your M4B file above and Morphio decodes it locally, then re-encodes it as M4A using WebAssembly + the browser's native codecs. Nothing is ever uploaded — your files stay on your device. Batch as many files as your machine can handle. See exactly how in-browser conversion works.
Open the M4B to M4A page, drop your audio file on the drop zone and press convert. Morphio runs an FFmpeg build compiled to WebAssembly that runs inside the page, so the M4B data never leaves your device and no server ever receives a copy.
Sample rate and channel layout carry across, and you keep the original file untouched on disk. Converting M4B to M4A only rewrites the container and encoding you asked for — the source file on your disk is never modified.
Yes. The free plan covers 10 conversions a day with files up to 200 MB and adds no watermark or sign-up. Morphio Pro ($5/month, or $29 once for lifetime access) removes the daily cap and raises the per-file limit to 5 GB.
Morphio decodes the M4B file at full fidelity and re-encodes it at a high-quality M4A setting, so the difference is normally invisible or inaudible. What conversion cannot do is recover detail the original M4B file already threw away.
Yes — drop the whole batch in and each file is processed in turn on your own machine. The practical limit is your device's memory and patience, not a server quota, because nothing is queued anywhere else.
No. The conversion runs entirely inside your browser using WebAssembly, so the file never leaves your device — you can disconnect from the internet after the page loads and it still works.