Audio tool

Convert AAC Files to M4B on Your Device

Convert AAC to M4B in your browser for spoken-word publishing. The source remains on your device throughout local processing.

Route AAC → M4B

or drop here · up to 500 MB

Max 50 MB per file

Preview (optional)

When your browser supports it, your audio plays here. You can still convert your file if preview does not load.

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Use upload name

On-device encoding can work the processor harder than ordinary playback during this AAC-to-M4B job.
Long AAC files consume more memory and take longer to decode.
Check picture, sound, and timing in M4B before removing the source.

M4B serves audiobooks and chapter-aware Apple playback, whereas AAC commonly serves streaming, mobile playback, and compact delivery.
For AAC-to-M4B delivery, plan for chapter metadata varying by player.
After leaving AAC, the receiving app must support the streams encoded inside M4B, not only its extension.

AAC to M4B taking too long? Free local memory and keep the conversion tab in the foreground.
M4B converted from AAC not opening? Test a compatible player and inspect the output streams.
Inspect the generated streams when an app recognizes M4B but refuses playback.

When does AAC to M4B conversion make sense?

It is useful when AAC media created for efficient distribution must enter a M4B system designed for spoken-word publishing.

Where is the AAC source processed?

The browser prepares M4B from AAC on this device instead of sending the source to a remote conversion server.

How can I approve M4B converted from AAC?

Test the M4B file in the receiving app and compare duration, channels and loudness with the AAC source.

Quick use cases